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Home / DTC / P0731 — Gear 1 Incorrect Ratio

P0731 — Gear 1 Incorrect Ratio

Detailed page for trouble code P0731.

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Code

P0731

Generic P — Powertrain

Gear 1 Incorrect Ratio

Brand: Generic
Type: P — Powertrain
Views: UK: 39 EN: 56 RU: 89
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Low or contaminated automatic transmission fluid (ATF) causing poor hydraulic pressure
  • Faulty or sticking shift solenoid(s) that control 1st gear
  • Worn or burned 1st gear clutch pack or band slipping
  • Damaged planetary gear set or internal transmission components
  • Faulty input/output (shaft) speed sensors or bad sensor signals
  • Valve body failure or sticking valves

Symptoms

  • Check Engine Light / MIL illuminated
  • Harsh, delayed or erratic shifts into 1st gear
  • Engine revs high without expected vehicle acceleration (slipping) in 1st
  • Transmission may go into limp mode
  • Loss of drive or poor acceleration from a stop
  • Burning smell if clutches are slipping severely

What to check

  • Retrieve freeze-frame data and all stored codes; note related transmission codes
  • Compare commanded gear with actual gear (read gear ratio or shaft speeds) using a scan tool during a road test
  • Check ATF level and condition (color, odor, particles) with warm engine per vehicle procedure
  • Inspect wiring and connectors for transmission speed sensors and solenoids for damage or corrosion
  • Monitor input shaft speed (ISS), output shaft speed (OSS)/vehicle speed, engine RPM, and TCM commanded gear
  • Check transmission line pressure with a gauge (manufacturer procedure) to verify hydraulic pressure

Signal parameters

  • Engine RPM (crankshaft) — should correlate with input shaft speed when clutch locked
  • Input shaft speed (ISS) — expected to rise proportionally in 1st gear
  • Output shaft speed / Vehicle speed sensor (OSS/VSS) — used to calculate actual gear ratio
  • Commanded gear from TCM — should indicate gear 1 during test
  • Calculated gear ratio = ISS / OSS (should match manufacturer first-gear specification)
  • Shift solenoid status (ON/OFF) and duty cycle — compare to commanded shifts

Diagnostic algorithm

  1. Read and record all DTCs and freeze-frame data. Clear codes and perform a controlled road test while monitoring live data to attempt to re-create the fault.
  2. Verify the vehicle is in the correct operating conditions (ATF temp, load, throttle) while testing. Observe commanded gear vs actual ISS/OSS ratio during engagement of 1st gear.
  3. Check ATF level and condition; correct level or replace fluid/filter if contaminated. Recheck for recurrence.
  4. Inspect wiring and connectors for the transmission speed sensors and shift solenoids; repair any damaged wiring or poor connections.
  5. Using a scan tool, test shift solenoid(s) for correct resistance and operation. Activate solenoids while monitoring pressure/gear response.
  6. Measure transmission line pressure per manufacturer procedure. Low pressure indicates hydraulic faults (pump, valves, worn clutches).
  7. If electrical and hydraulic checks pass, remove transmission pan and inspect for metal debris, clutch material, or valve body issues. Replace or rebuild damaged components as required.
  8. If internal mechanical damage is suspected (worn clutch pack, broken gear, or planetary set), disassemble transmission for internal inspection and repair or rebuild.
  9. After repairs, clear codes and perform a full road test with live data to confirm the calculated gear ratio matches specification and the P0731 does not return.
  10. Check for any available manufacturer TSBs or software updates and reflash TCM if recommended.

Likely causes

  • Low/contaminated ATF or incorrect fluid level
  • Sticking or failed shift solenoid(s) for 1st gear
  • Worn 1st gear clutch pack or slipping friction material
  • Valve body or hydraulic control problem
  • Faulty input or output speed sensor or damaged wiring

Fault status

⚠️ Status
P0731 — Transmission 1st gear ratio is incorrect. The control module detected a mismatch between expected and actual input/output speeds for first gear, suggesting a hydraulic, mechanical, sensor, or control issue.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-6 hours

Similar codes

P0730 P0732 P0733 P0734 P0735 P0736
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Code

P0731

GWM P — Powertrain

- 1 gear is not adjusted correctly

Brand: GWM
Type: P — Powertrain
Views: UK: 27 EN: 52 RU: 37
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Low or contaminated automatic transmission fluid (ATF) causing poor hydraulic pressure
  • Faulty or sticking shift solenoid(s) that control 1st gear
  • Worn or burned 1st gear clutch pack or band slipping
  • Damaged planetary gear set or internal transmission components
  • Faulty input/output (shaft) speed sensors or bad sensor signals
  • Valve body failure or sticking valves

Symptoms

  • Check Engine Light / MIL illuminated
  • Harsh, delayed or erratic shifts into 1st gear
  • Engine revs high without expected vehicle acceleration (slipping) in 1st
  • Transmission may go into limp mode
  • Loss of drive or poor acceleration from a stop
  • Burning smell if clutches are slipping severely

What to check

  • Retrieve freeze-frame data and all stored codes; note related transmission codes
  • Compare commanded gear with actual gear (read gear ratio or shaft speeds) using a scan tool during a road test
  • Check ATF level and condition (color, odor, particles) with warm engine per vehicle procedure
  • Inspect wiring and connectors for transmission speed sensors and solenoids for damage or corrosion
  • Monitor input shaft speed (ISS), output shaft speed (OSS)/vehicle speed, engine RPM, and TCM commanded gear
  • Check transmission line pressure with a gauge (manufacturer procedure) to verify hydraulic pressure

Signal parameters

  • Engine RPM (crankshaft) — should correlate with input shaft speed when clutch locked
  • Input shaft speed (ISS) — expected to rise proportionally in 1st gear
  • Output shaft speed / Vehicle speed sensor (OSS/VSS) — used to calculate actual gear ratio
  • Commanded gear from TCM — should indicate gear 1 during test
  • Calculated gear ratio = ISS / OSS (should match manufacturer first-gear specification)
  • Shift solenoid status (ON/OFF) and duty cycle — compare to commanded shifts

Diagnostic algorithm

  1. Read and record all DTCs and freeze-frame data. Clear codes and perform a controlled road test while monitoring live data to attempt to re-create the fault.
  2. Verify the vehicle is in the correct operating conditions (ATF temp, load, throttle) while testing. Observe commanded gear vs actual ISS/OSS ratio during engagement of 1st gear.
  3. Check ATF level and condition; correct level or replace fluid/filter if contaminated. Recheck for recurrence.
  4. Inspect wiring and connectors for the transmission speed sensors and shift solenoids; repair any damaged wiring or poor connections.
  5. Using a scan tool, test shift solenoid(s) for correct resistance and operation. Activate solenoids while monitoring pressure/gear response.
  6. Measure transmission line pressure per manufacturer procedure. Low pressure indicates hydraulic faults (pump, valves, worn clutches).
  7. If electrical and hydraulic checks pass, remove transmission pan and inspect for metal debris, clutch material, or valve body issues. Replace or rebuild damaged components as required.
  8. If internal mechanical damage is suspected (worn clutch pack, broken gear, or planetary set), disassemble transmission for internal inspection and repair or rebuild.
  9. After repairs, clear codes and perform a full road test with live data to confirm the calculated gear ratio matches specification and the P0731 does not return.
  10. Check for any available manufacturer TSBs or software updates and reflash TCM if recommended.

Likely causes

  • Low/contaminated ATF or incorrect fluid level
  • Sticking or failed shift solenoid(s) for 1st gear
  • Worn 1st gear clutch pack or slipping friction material
  • Valve body or hydraulic control problem
  • Faulty input or output speed sensor or damaged wiring

Fault status

⚠️ Status
P0731 — Transmission 1st gear ratio is incorrect. The control module detected a mismatch between expected and actual input/output speeds for first gear, suggesting a hydraulic, mechanical, sensor, or control issue.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-6 hours

Similar codes

P0730 P0732 P0733 P0734 P0735 P0736
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Code

P0731

HUMMER P — Powertrain

Incorrect 1st Gear Ratio

Brand: HUMMER
Type: P — Powertrain
Views: UK: 25 EN: 48 RU: 57
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Low or contaminated automatic transmission fluid (ATF) causing poor hydraulic pressure
  • Faulty or sticking shift solenoid(s) that control 1st gear
  • Worn or burned 1st gear clutch pack or band slipping
  • Damaged planetary gear set or internal transmission components
  • Faulty input/output (shaft) speed sensors or bad sensor signals
  • Valve body failure or sticking valves

Symptoms

  • Check Engine Light / MIL illuminated
  • Harsh, delayed or erratic shifts into 1st gear
  • Engine revs high without expected vehicle acceleration (slipping) in 1st
  • Transmission may go into limp mode
  • Loss of drive or poor acceleration from a stop
  • Burning smell if clutches are slipping severely

What to check

  • Retrieve freeze-frame data and all stored codes; note related transmission codes
  • Compare commanded gear with actual gear (read gear ratio or shaft speeds) using a scan tool during a road test
  • Check ATF level and condition (color, odor, particles) with warm engine per vehicle procedure
  • Inspect wiring and connectors for transmission speed sensors and solenoids for damage or corrosion
  • Monitor input shaft speed (ISS), output shaft speed (OSS)/vehicle speed, engine RPM, and TCM commanded gear
  • Check transmission line pressure with a gauge (manufacturer procedure) to verify hydraulic pressure

Signal parameters

  • Engine RPM (crankshaft) — should correlate with input shaft speed when clutch locked
  • Input shaft speed (ISS) — expected to rise proportionally in 1st gear
  • Output shaft speed / Vehicle speed sensor (OSS/VSS) — used to calculate actual gear ratio
  • Commanded gear from TCM — should indicate gear 1 during test
  • Calculated gear ratio = ISS / OSS (should match manufacturer first-gear specification)
  • Shift solenoid status (ON/OFF) and duty cycle — compare to commanded shifts

Diagnostic algorithm

  1. Read and record all DTCs and freeze-frame data. Clear codes and perform a controlled road test while monitoring live data to attempt to re-create the fault.
  2. Verify the vehicle is in the correct operating conditions (ATF temp, load, throttle) while testing. Observe commanded gear vs actual ISS/OSS ratio during engagement of 1st gear.
  3. Check ATF level and condition; correct level or replace fluid/filter if contaminated. Recheck for recurrence.
  4. Inspect wiring and connectors for the transmission speed sensors and shift solenoids; repair any damaged wiring or poor connections.
  5. Using a scan tool, test shift solenoid(s) for correct resistance and operation. Activate solenoids while monitoring pressure/gear response.
  6. Measure transmission line pressure per manufacturer procedure. Low pressure indicates hydraulic faults (pump, valves, worn clutches).
  7. If electrical and hydraulic checks pass, remove transmission pan and inspect for metal debris, clutch material, or valve body issues. Replace or rebuild damaged components as required.
  8. If internal mechanical damage is suspected (worn clutch pack, broken gear, or planetary set), disassemble transmission for internal inspection and repair or rebuild.
  9. After repairs, clear codes and perform a full road test with live data to confirm the calculated gear ratio matches specification and the P0731 does not return.
  10. Check for any available manufacturer TSBs or software updates and reflash TCM if recommended.

Likely causes

  • Low/contaminated ATF or incorrect fluid level
  • Sticking or failed shift solenoid(s) for 1st gear
  • Worn 1st gear clutch pack or slipping friction material
  • Valve body or hydraulic control problem
  • Faulty input or output speed sensor or damaged wiring

Fault status

⚠️ Status
P0731 — Transmission 1st gear ratio is incorrect. The control module detected a mismatch between expected and actual input/output speeds for first gear, suggesting a hydraulic, mechanical, sensor, or control issue.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-6 hours

Similar codes

P0730 P0732 P0733 P0734 P0735 P0736
Repair manuals

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Code

P0731

LAND ROVER P — Powertrain

Incorrect Gear Ratio 1

Brand: LAND ROVER
Type: P — Powertrain
Views: UK: 21 EN: 43 RU: 49
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Low or contaminated automatic transmission fluid (ATF) causing poor hydraulic pressure
  • Faulty or sticking shift solenoid(s) that control 1st gear
  • Worn or burned 1st gear clutch pack or band slipping
  • Damaged planetary gear set or internal transmission components
  • Faulty input/output (shaft) speed sensors or bad sensor signals
  • Valve body failure or sticking valves

Symptoms

  • Check Engine Light / MIL illuminated
  • Harsh, delayed or erratic shifts into 1st gear
  • Engine revs high without expected vehicle acceleration (slipping) in 1st
  • Transmission may go into limp mode
  • Loss of drive or poor acceleration from a stop
  • Burning smell if clutches are slipping severely

What to check

  • Retrieve freeze-frame data and all stored codes; note related transmission codes
  • Compare commanded gear with actual gear (read gear ratio or shaft speeds) using a scan tool during a road test
  • Check ATF level and condition (color, odor, particles) with warm engine per vehicle procedure
  • Inspect wiring and connectors for transmission speed sensors and solenoids for damage or corrosion
  • Monitor input shaft speed (ISS), output shaft speed (OSS)/vehicle speed, engine RPM, and TCM commanded gear
  • Check transmission line pressure with a gauge (manufacturer procedure) to verify hydraulic pressure

Signal parameters

  • Engine RPM (crankshaft) — should correlate with input shaft speed when clutch locked
  • Input shaft speed (ISS) — expected to rise proportionally in 1st gear
  • Output shaft speed / Vehicle speed sensor (OSS/VSS) — used to calculate actual gear ratio
  • Commanded gear from TCM — should indicate gear 1 during test
  • Calculated gear ratio = ISS / OSS (should match manufacturer first-gear specification)
  • Shift solenoid status (ON/OFF) and duty cycle — compare to commanded shifts

Diagnostic algorithm

  1. Read and record all DTCs and freeze-frame data. Clear codes and perform a controlled road test while monitoring live data to attempt to re-create the fault.
  2. Verify the vehicle is in the correct operating conditions (ATF temp, load, throttle) while testing. Observe commanded gear vs actual ISS/OSS ratio during engagement of 1st gear.
  3. Check ATF level and condition; correct level or replace fluid/filter if contaminated. Recheck for recurrence.
  4. Inspect wiring and connectors for the transmission speed sensors and shift solenoids; repair any damaged wiring or poor connections.
  5. Using a scan tool, test shift solenoid(s) for correct resistance and operation. Activate solenoids while monitoring pressure/gear response.
  6. Measure transmission line pressure per manufacturer procedure. Low pressure indicates hydraulic faults (pump, valves, worn clutches).
  7. If electrical and hydraulic checks pass, remove transmission pan and inspect for metal debris, clutch material, or valve body issues. Replace or rebuild damaged components as required.
  8. If internal mechanical damage is suspected (worn clutch pack, broken gear, or planetary set), disassemble transmission for internal inspection and repair or rebuild.
  9. After repairs, clear codes and perform a full road test with live data to confirm the calculated gear ratio matches specification and the P0731 does not return.
  10. Check for any available manufacturer TSBs or software updates and reflash TCM if recommended.

Likely causes

  • Low/contaminated ATF or incorrect fluid level
  • Sticking or failed shift solenoid(s) for 1st gear
  • Worn 1st gear clutch pack or slipping friction material
  • Valve body or hydraulic control problem
  • Faulty input or output speed sensor or damaged wiring

Fault status

⚠️ Status
P0731 — Transmission 1st gear ratio is incorrect. The control module detected a mismatch between expected and actual input/output speeds for first gear, suggesting a hydraulic, mechanical, sensor, or control issue.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-6 hours

Similar codes

P0730 P0732 P0733 P0734 P0735 P0736
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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Code

P0731

MERCEDES-BENZ P — Powertrain

Gear 1 Incorrect ratio

Brand: MERCEDES-BENZ
Type: P — Powertrain
Views: UK: 34 EN: 57 RU: 61
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Low or contaminated automatic transmission fluid (ATF) causing poor hydraulic pressure
  • Faulty or sticking shift solenoid(s) that control 1st gear
  • Worn or burned 1st gear clutch pack or band slipping
  • Damaged planetary gear set or internal transmission components
  • Faulty input/output (shaft) speed sensors or bad sensor signals
  • Valve body failure or sticking valves

Symptoms

  • Check Engine Light / MIL illuminated
  • Harsh, delayed or erratic shifts into 1st gear
  • Engine revs high without expected vehicle acceleration (slipping) in 1st
  • Transmission may go into limp mode
  • Loss of drive or poor acceleration from a stop
  • Burning smell if clutches are slipping severely

What to check

  • Retrieve freeze-frame data and all stored codes; note related transmission codes
  • Compare commanded gear with actual gear (read gear ratio or shaft speeds) using a scan tool during a road test
  • Check ATF level and condition (color, odor, particles) with warm engine per vehicle procedure
  • Inspect wiring and connectors for transmission speed sensors and solenoids for damage or corrosion
  • Monitor input shaft speed (ISS), output shaft speed (OSS)/vehicle speed, engine RPM, and TCM commanded gear
  • Check transmission line pressure with a gauge (manufacturer procedure) to verify hydraulic pressure

Signal parameters

  • Engine RPM (crankshaft) — should correlate with input shaft speed when clutch locked
  • Input shaft speed (ISS) — expected to rise proportionally in 1st gear
  • Output shaft speed / Vehicle speed sensor (OSS/VSS) — used to calculate actual gear ratio
  • Commanded gear from TCM — should indicate gear 1 during test
  • Calculated gear ratio = ISS / OSS (should match manufacturer first-gear specification)
  • Shift solenoid status (ON/OFF) and duty cycle — compare to commanded shifts

Diagnostic algorithm

  1. Read and record all DTCs and freeze-frame data. Clear codes and perform a controlled road test while monitoring live data to attempt to re-create the fault.
  2. Verify the vehicle is in the correct operating conditions (ATF temp, load, throttle) while testing. Observe commanded gear vs actual ISS/OSS ratio during engagement of 1st gear.
  3. Check ATF level and condition; correct level or replace fluid/filter if contaminated. Recheck for recurrence.
  4. Inspect wiring and connectors for the transmission speed sensors and shift solenoids; repair any damaged wiring or poor connections.
  5. Using a scan tool, test shift solenoid(s) for correct resistance and operation. Activate solenoids while monitoring pressure/gear response.
  6. Measure transmission line pressure per manufacturer procedure. Low pressure indicates hydraulic faults (pump, valves, worn clutches).
  7. If electrical and hydraulic checks pass, remove transmission pan and inspect for metal debris, clutch material, or valve body issues. Replace or rebuild damaged components as required.
  8. If internal mechanical damage is suspected (worn clutch pack, broken gear, or planetary set), disassemble transmission for internal inspection and repair or rebuild.
  9. After repairs, clear codes and perform a full road test with live data to confirm the calculated gear ratio matches specification and the P0731 does not return.
  10. Check for any available manufacturer TSBs or software updates and reflash TCM if recommended.

Likely causes

  • Low/contaminated ATF or incorrect fluid level
  • Sticking or failed shift solenoid(s) for 1st gear
  • Worn 1st gear clutch pack or slipping friction material
  • Valve body or hydraulic control problem
  • Faulty input or output speed sensor or damaged wiring

Fault status

⚠️ Status
P0731 — Transmission 1st gear ratio is incorrect. The control module detected a mismatch between expected and actual input/output speeds for first gear, suggesting a hydraulic, mechanical, sensor, or control issue.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-6 hours

Similar codes

P0730 P0732 P0733 P0734 P0735 P0736
610

Browse 610 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MERCEDES-BENZ

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Code

P0731

MITSUBISHI P — Powertrain

Gear shift 1st incomplete

Brand: MITSUBISHI
Type: P — Powertrain
Views: UK: 23 EN: 42 RU: 53
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Low or contaminated automatic transmission fluid (ATF) causing poor hydraulic pressure
  • Faulty or sticking shift solenoid(s) that control 1st gear
  • Worn or burned 1st gear clutch pack or band slipping
  • Damaged planetary gear set or internal transmission components
  • Faulty input/output (shaft) speed sensors or bad sensor signals
  • Valve body failure or sticking valves

Symptoms

  • Check Engine Light / MIL illuminated
  • Harsh, delayed or erratic shifts into 1st gear
  • Engine revs high without expected vehicle acceleration (slipping) in 1st
  • Transmission may go into limp mode
  • Loss of drive or poor acceleration from a stop
  • Burning smell if clutches are slipping severely

What to check

  • Retrieve freeze-frame data and all stored codes; note related transmission codes
  • Compare commanded gear with actual gear (read gear ratio or shaft speeds) using a scan tool during a road test
  • Check ATF level and condition (color, odor, particles) with warm engine per vehicle procedure
  • Inspect wiring and connectors for transmission speed sensors and solenoids for damage or corrosion
  • Monitor input shaft speed (ISS), output shaft speed (OSS)/vehicle speed, engine RPM, and TCM commanded gear
  • Check transmission line pressure with a gauge (manufacturer procedure) to verify hydraulic pressure

Signal parameters

  • Engine RPM (crankshaft) — should correlate with input shaft speed when clutch locked
  • Input shaft speed (ISS) — expected to rise proportionally in 1st gear
  • Output shaft speed / Vehicle speed sensor (OSS/VSS) — used to calculate actual gear ratio
  • Commanded gear from TCM — should indicate gear 1 during test
  • Calculated gear ratio = ISS / OSS (should match manufacturer first-gear specification)
  • Shift solenoid status (ON/OFF) and duty cycle — compare to commanded shifts

Diagnostic algorithm

  1. Read and record all DTCs and freeze-frame data. Clear codes and perform a controlled road test while monitoring live data to attempt to re-create the fault.
  2. Verify the vehicle is in the correct operating conditions (ATF temp, load, throttle) while testing. Observe commanded gear vs actual ISS/OSS ratio during engagement of 1st gear.
  3. Check ATF level and condition; correct level or replace fluid/filter if contaminated. Recheck for recurrence.
  4. Inspect wiring and connectors for the transmission speed sensors and shift solenoids; repair any damaged wiring or poor connections.
  5. Using a scan tool, test shift solenoid(s) for correct resistance and operation. Activate solenoids while monitoring pressure/gear response.
  6. Measure transmission line pressure per manufacturer procedure. Low pressure indicates hydraulic faults (pump, valves, worn clutches).
  7. If electrical and hydraulic checks pass, remove transmission pan and inspect for metal debris, clutch material, or valve body issues. Replace or rebuild damaged components as required.
  8. If internal mechanical damage is suspected (worn clutch pack, broken gear, or planetary set), disassemble transmission for internal inspection and repair or rebuild.
  9. After repairs, clear codes and perform a full road test with live data to confirm the calculated gear ratio matches specification and the P0731 does not return.
  10. Check for any available manufacturer TSBs or software updates and reflash TCM if recommended.

Likely causes

  • Low/contaminated ATF or incorrect fluid level
  • Sticking or failed shift solenoid(s) for 1st gear
  • Worn 1st gear clutch pack or slipping friction material
  • Valve body or hydraulic control problem
  • Faulty input or output speed sensor or damaged wiring

Fault status

⚠️ Status
P0731 — Transmission 1st gear ratio is incorrect. The control module detected a mismatch between expected and actual input/output speeds for first gear, suggesting a hydraulic, mechanical, sensor, or control issue.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-6 hours

Similar codes

P0730 P0732 P0733 P0734 P0735 P0736
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MITSUBISHI

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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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