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Home / DTC / P0789 — Shift Timing Solenoid A Intermittent

P0789 — Shift Timing Solenoid A Intermittent

Detailed page for trouble code P0789.

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11,608generic
22,491specific
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Code

P0789

Generic P — Powertrain

Shift Timing Solenoid A Intermittent

Brand: Generic
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

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

  1. Confirm the code and capture freeze-frame / live data. Note when and under what conditions the fault occurred.
  2. Inspect transmission fluid level and condition. Replace fluid/filter if heavily contaminated before further testing.
  3. Visually inspect the wiring harness and connectors for the Shift Timing Solenoid A. Repair any damaged wiring, pins or connectors.
  4. 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.
  5. Perform a wiggle test on harness and connector while monitoring live data to try to reproduce the intermittent fault.
  6. Measure coil resistance of the solenoid. If out of range or fluctuating, replace solenoid.
  7. If wiring and solenoid seem good, check voltage drop on power and ground circuits under load and inspect transmission grounds.
  8. 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.
  9. 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.
  10. 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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P0760 P0761 P0780 P0790 P0776 P2767
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Code

P0789

GWM P — Powertrain

- Solenoid fault

Brand: GWM
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

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

  1. Confirm the code and capture freeze-frame / live data. Note when and under what conditions the fault occurred.
  2. Inspect transmission fluid level and condition. Replace fluid/filter if heavily contaminated before further testing.
  3. Visually inspect the wiring harness and connectors for the Shift Timing Solenoid A. Repair any damaged wiring, pins or connectors.
  4. 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.
  5. Perform a wiggle test on harness and connector while monitoring live data to try to reproduce the intermittent fault.
  6. Measure coil resistance of the solenoid. If out of range or fluctuating, replace solenoid.
  7. If wiring and solenoid seem good, check voltage drop on power and ground circuits under load and inspect transmission grounds.
  8. 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.
  9. 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.
  10. 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

P0760 P0761 P0780 P0790 P0776 P2767
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Code

P0789

HUMMER P — Powertrain

Shift/Timing Solenoid Intermittent

Brand: HUMMER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

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

  1. Confirm the code and capture freeze-frame / live data. Note when and under what conditions the fault occurred.
  2. Inspect transmission fluid level and condition. Replace fluid/filter if heavily contaminated before further testing.
  3. Visually inspect the wiring harness and connectors for the Shift Timing Solenoid A. Repair any damaged wiring, pins or connectors.
  4. 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.
  5. Perform a wiggle test on harness and connector while monitoring live data to try to reproduce the intermittent fault.
  6. Measure coil resistance of the solenoid. If out of range or fluctuating, replace solenoid.
  7. If wiring and solenoid seem good, check voltage drop on power and ground circuits under load and inspect transmission grounds.
  8. 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.
  9. 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.
  10. 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

P0760 P0761 P0780 P0790 P0776 P2767
Repair manuals

Manual library for HUMMER

138

Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

HUMMER

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Code

P0789

MERCEDES-BENZ P — Powertrain

Shift/Timing Solenoid Intermittent

Brand: MERCEDES-BENZ
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

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

  1. Confirm the code and capture freeze-frame / live data. Note when and under what conditions the fault occurred.
  2. Inspect transmission fluid level and condition. Replace fluid/filter if heavily contaminated before further testing.
  3. Visually inspect the wiring harness and connectors for the Shift Timing Solenoid A. Repair any damaged wiring, pins or connectors.
  4. 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.
  5. Perform a wiggle test on harness and connector while monitoring live data to try to reproduce the intermittent fault.
  6. Measure coil resistance of the solenoid. If out of range or fluctuating, replace solenoid.
  7. If wiring and solenoid seem good, check voltage drop on power and ground circuits under load and inspect transmission grounds.
  8. 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.
  9. 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.
  10. 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

P0760 P0761 P0780 P0790 P0776 P2767
856

Browse 856 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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