Code
P0789
Generic
P — Powertrain
Shift Timing Solenoid A Intermittent
Views:
UK: 17
EN: 20
RU: 17
AI status
Completed
Completed
100%
Causes
- Intermittent open, short or high-resistance in wiring to Shift Timing Solenoid A
- Loose, corroded or damaged connector/pins at solenoid or TCM
- Faulty Shift Timing Solenoid A (intermittent internal failure)
- Contaminated or degraded transmission fluid causing valve sticking
- Sticking valve in the valve body or internal hydraulic issue
- Poor ground or intermittent power supply to solenoid
Symptoms
- Check Engine / MIL illuminated (transmission-related DTC)
- Intermittent harsh, delayed or erratic shifts
- Transmission may hunt between gears or hesitate during shifts
- Possible limp-in mode or reduced shift functionality when fault active
- No consistent fault — drivability may be normal between occurrences
What to check
- Read freeze frame and live data; note conditions when code set (temperature, load, gear, speed)
- Scan for related transmission codes and vehicle manufacturer-specific codes
- Visually inspect transmission fluid level/condition for contamination or burnt smell
- Inspect connector at Shift Timing Solenoid A and harness for corrosion, looseness, chafing or water intrusion
- Perform wiggle test of wiring and connector while monitoring live solenoid status to reproduce intermittent
- Measure solenoid coil resistance with multimeter (at ambient) and compare to spec
Signal parameters
- Coil resistance (typical, vehicle-dependent): roughly 8–30 ohms at 20°C — consult vehicle spec
- Supply voltage when commanded (pulsed/PWM): near battery voltage on power feed; duty cycle varies with control strategy
- PWM frequency (if used): commonly tens to a few hundred Hz depending on design (vehicle-specific)
- Expected behavior: stable commanded duty/pulse and correlated hydraulic/shift response; intermittent or noisy voltage indicates problem
Diagnostic algorithm
- Confirm the code and capture freeze-frame / live data. Note when and under what conditions the fault occurred.
- Inspect transmission fluid level and condition. Replace fluid/filter if heavily contaminated before further testing.
- Visually inspect the wiring harness and connectors for the Shift Timing Solenoid A. Repair any damaged wiring, pins or connectors.
- Backprobe the solenoid connector. With the engine/ignition and transmission in the required state, monitor supply voltage and ground while commanding the solenoid with a scan tool. Look for intermittent loss of voltage or ground.
- Perform a wiggle test on harness and connector while monitoring live data to try to reproduce the intermittent fault.
- Measure coil resistance of the solenoid. If out of range or fluctuating, replace solenoid.
- If wiring and solenoid seem good, check voltage drop on power and ground circuits under load and inspect transmission grounds.
- If electrical system checks pass but intermittent still occurs, consider valve body inspection for sticking valves or internal hydraulic issues; perform valve body service or solenoid replacement as appropriate.
- If all mechanical and electrical items check OK, consult manufacturer diagnostics for TCM output testing; consider reflashing or replacing TCM if tests indicate controller fault.
- After repairs, clear codes and road-test to confirm the intermittent condition is resolved. Monitor live data for recurrence.
Likely causes
- Wiring harness damage or intermittent connector contact to solenoid
- Corroded connector pin or poor pin fit causing intermittent contact
- Solenoid beginning to fail (intermittent operation)
- Valve body contamination/sticking causing intermittent hydraulic response
Fault status
Status
Intermittent electrical/performance fault detected for Shift Timing Solenoid A. Condition was present momentarily and may not be currently active.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P0789
GWM
P — Powertrain
- Solenoid fault
Views:
UK: 2
EN: 2
RU: 1
AI status
Completed
Completed
100%
Causes
- Intermittent open, short or high-resistance in wiring to Shift Timing Solenoid A
- Loose, corroded or damaged connector/pins at solenoid or TCM
- Faulty Shift Timing Solenoid A (intermittent internal failure)
- Contaminated or degraded transmission fluid causing valve sticking
- Sticking valve in the valve body or internal hydraulic issue
- Poor ground or intermittent power supply to solenoid
Symptoms
- Check Engine / MIL illuminated (transmission-related DTC)
- Intermittent harsh, delayed or erratic shifts
- Transmission may hunt between gears or hesitate during shifts
- Possible limp-in mode or reduced shift functionality when fault active
- No consistent fault — drivability may be normal between occurrences
What to check
- Read freeze frame and live data; note conditions when code set (temperature, load, gear, speed)
- Scan for related transmission codes and vehicle manufacturer-specific codes
- Visually inspect transmission fluid level/condition for contamination or burnt smell
- Inspect connector at Shift Timing Solenoid A and harness for corrosion, looseness, chafing or water intrusion
- Perform wiggle test of wiring and connector while monitoring live solenoid status to reproduce intermittent
- Measure solenoid coil resistance with multimeter (at ambient) and compare to spec
Signal parameters
- Coil resistance (typical, vehicle-dependent): roughly 8–30 ohms at 20°C — consult vehicle spec
- Supply voltage when commanded (pulsed/PWM): near battery voltage on power feed; duty cycle varies with control strategy
- PWM frequency (if used): commonly tens to a few hundred Hz depending on design (vehicle-specific)
- Expected behavior: stable commanded duty/pulse and correlated hydraulic/shift response; intermittent or noisy voltage indicates problem
Diagnostic algorithm
- Confirm the code and capture freeze-frame / live data. Note when and under what conditions the fault occurred.
- Inspect transmission fluid level and condition. Replace fluid/filter if heavily contaminated before further testing.
- Visually inspect the wiring harness and connectors for the Shift Timing Solenoid A. Repair any damaged wiring, pins or connectors.
- Backprobe the solenoid connector. With the engine/ignition and transmission in the required state, monitor supply voltage and ground while commanding the solenoid with a scan tool. Look for intermittent loss of voltage or ground.
- Perform a wiggle test on harness and connector while monitoring live data to try to reproduce the intermittent fault.
- Measure coil resistance of the solenoid. If out of range or fluctuating, replace solenoid.
- If wiring and solenoid seem good, check voltage drop on power and ground circuits under load and inspect transmission grounds.
- If electrical system checks pass but intermittent still occurs, consider valve body inspection for sticking valves or internal hydraulic issues; perform valve body service or solenoid replacement as appropriate.
- If all mechanical and electrical items check OK, consult manufacturer diagnostics for TCM output testing; consider reflashing or replacing TCM if tests indicate controller fault.
- After repairs, clear codes and road-test to confirm the intermittent condition is resolved. Monitor live data for recurrence.
Likely causes
- Wiring harness damage or intermittent connector contact to solenoid
- Corroded connector pin or poor pin fit causing intermittent contact
- Solenoid beginning to fail (intermittent operation)
- Valve body contamination/sticking causing intermittent hydraulic response
Fault status
Status
Intermittent electrical/performance fault detected for Shift Timing Solenoid A. Condition was present momentarily and may not be currently active.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P0789
HUMMER
P — Powertrain
Shift/Timing Solenoid Intermittent
Views:
UK: 11
EN: 11
RU: 10
AI status
Completed
Completed
100%
Causes
- Intermittent open, short or high-resistance in wiring to Shift Timing Solenoid A
- Loose, corroded or damaged connector/pins at solenoid or TCM
- Faulty Shift Timing Solenoid A (intermittent internal failure)
- Contaminated or degraded transmission fluid causing valve sticking
- Sticking valve in the valve body or internal hydraulic issue
- Poor ground or intermittent power supply to solenoid
Symptoms
- Check Engine / MIL illuminated (transmission-related DTC)
- Intermittent harsh, delayed or erratic shifts
- Transmission may hunt between gears or hesitate during shifts
- Possible limp-in mode or reduced shift functionality when fault active
- No consistent fault — drivability may be normal between occurrences
What to check
- Read freeze frame and live data; note conditions when code set (temperature, load, gear, speed)
- Scan for related transmission codes and vehicle manufacturer-specific codes
- Visually inspect transmission fluid level/condition for contamination or burnt smell
- Inspect connector at Shift Timing Solenoid A and harness for corrosion, looseness, chafing or water intrusion
- Perform wiggle test of wiring and connector while monitoring live solenoid status to reproduce intermittent
- Measure solenoid coil resistance with multimeter (at ambient) and compare to spec
Signal parameters
- Coil resistance (typical, vehicle-dependent): roughly 8–30 ohms at 20°C — consult vehicle spec
- Supply voltage when commanded (pulsed/PWM): near battery voltage on power feed; duty cycle varies with control strategy
- PWM frequency (if used): commonly tens to a few hundred Hz depending on design (vehicle-specific)
- Expected behavior: stable commanded duty/pulse and correlated hydraulic/shift response; intermittent or noisy voltage indicates problem
Diagnostic algorithm
- Confirm the code and capture freeze-frame / live data. Note when and under what conditions the fault occurred.
- Inspect transmission fluid level and condition. Replace fluid/filter if heavily contaminated before further testing.
- Visually inspect the wiring harness and connectors for the Shift Timing Solenoid A. Repair any damaged wiring, pins or connectors.
- Backprobe the solenoid connector. With the engine/ignition and transmission in the required state, monitor supply voltage and ground while commanding the solenoid with a scan tool. Look for intermittent loss of voltage or ground.
- Perform a wiggle test on harness and connector while monitoring live data to try to reproduce the intermittent fault.
- Measure coil resistance of the solenoid. If out of range or fluctuating, replace solenoid.
- If wiring and solenoid seem good, check voltage drop on power and ground circuits under load and inspect transmission grounds.
- If electrical system checks pass but intermittent still occurs, consider valve body inspection for sticking valves or internal hydraulic issues; perform valve body service or solenoid replacement as appropriate.
- If all mechanical and electrical items check OK, consult manufacturer diagnostics for TCM output testing; consider reflashing or replacing TCM if tests indicate controller fault.
- After repairs, clear codes and road-test to confirm the intermittent condition is resolved. Monitor live data for recurrence.
Likely causes
- Wiring harness damage or intermittent connector contact to solenoid
- Corroded connector pin or poor pin fit causing intermittent contact
- Solenoid beginning to fail (intermittent operation)
- Valve body contamination/sticking causing intermittent hydraulic response
Fault status
Status
Intermittent electrical/performance fault detected for Shift Timing Solenoid A. Condition was present momentarily and may not be currently active.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P0789
MERCEDES-BENZ
P — Powertrain
Shift/Timing Solenoid Intermittent
Views:
UK: 15
EN: 13
RU: 13
AI status
Completed
Completed
100%
Causes
- Intermittent open, short or high-resistance in wiring to Shift Timing Solenoid A
- Loose, corroded or damaged connector/pins at solenoid or TCM
- Faulty Shift Timing Solenoid A (intermittent internal failure)
- Contaminated or degraded transmission fluid causing valve sticking
- Sticking valve in the valve body or internal hydraulic issue
- Poor ground or intermittent power supply to solenoid
Symptoms
- Check Engine / MIL illuminated (transmission-related DTC)
- Intermittent harsh, delayed or erratic shifts
- Transmission may hunt between gears or hesitate during shifts
- Possible limp-in mode or reduced shift functionality when fault active
- No consistent fault — drivability may be normal between occurrences
What to check
- Read freeze frame and live data; note conditions when code set (temperature, load, gear, speed)
- Scan for related transmission codes and vehicle manufacturer-specific codes
- Visually inspect transmission fluid level/condition for contamination or burnt smell
- Inspect connector at Shift Timing Solenoid A and harness for corrosion, looseness, chafing or water intrusion
- Perform wiggle test of wiring and connector while monitoring live solenoid status to reproduce intermittent
- Measure solenoid coil resistance with multimeter (at ambient) and compare to spec
Signal parameters
- Coil resistance (typical, vehicle-dependent): roughly 8–30 ohms at 20°C — consult vehicle spec
- Supply voltage when commanded (pulsed/PWM): near battery voltage on power feed; duty cycle varies with control strategy
- PWM frequency (if used): commonly tens to a few hundred Hz depending on design (vehicle-specific)
- Expected behavior: stable commanded duty/pulse and correlated hydraulic/shift response; intermittent or noisy voltage indicates problem
Diagnostic algorithm
- Confirm the code and capture freeze-frame / live data. Note when and under what conditions the fault occurred.
- Inspect transmission fluid level and condition. Replace fluid/filter if heavily contaminated before further testing.
- Visually inspect the wiring harness and connectors for the Shift Timing Solenoid A. Repair any damaged wiring, pins or connectors.
- Backprobe the solenoid connector. With the engine/ignition and transmission in the required state, monitor supply voltage and ground while commanding the solenoid with a scan tool. Look for intermittent loss of voltage or ground.
- Perform a wiggle test on harness and connector while monitoring live data to try to reproduce the intermittent fault.
- Measure coil resistance of the solenoid. If out of range or fluctuating, replace solenoid.
- If wiring and solenoid seem good, check voltage drop on power and ground circuits under load and inspect transmission grounds.
- If electrical system checks pass but intermittent still occurs, consider valve body inspection for sticking valves or internal hydraulic issues; perform valve body service or solenoid replacement as appropriate.
- If all mechanical and electrical items check OK, consult manufacturer diagnostics for TCM output testing; consider reflashing or replacing TCM if tests indicate controller fault.
- After repairs, clear codes and road-test to confirm the intermittent condition is resolved. Monitor live data for recurrence.
Likely causes
- Wiring harness damage or intermittent connector contact to solenoid
- Corroded connector pin or poor pin fit causing intermittent contact
- Solenoid beginning to fail (intermittent operation)
- Valve body contamination/sticking causing intermittent hydraulic response
Fault status
Status
Intermittent electrical/performance fault detected for Shift Timing Solenoid A. Condition was present momentarily and may not be currently active.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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👍 Like
0
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0
Send to email