Code
P0788
Generic
P — Powertrain
Shift Timing Solenoid A High
Views:
UK: 15
EN: 32
RU: 23
AI status
Completed
Completed
100%
Causes
- Short to battery/voltage in the solenoid control circuit
- Open or high-resistance ground in the solenoid circuit
- Failed shift timing solenoid (internal short or wiring fault)
- Damaged, corroded, or loose connector(s)
- Wiring chafing or pinched harness causing intermittent short
- Faulty TCM/PCM or poor driver transistor in control module
Symptoms
- Check Engine / Transmission warning light (MIL) illuminated
- Harsh, delayed, or erratic shifts
- Transmission may enter limp/reduced-gear mode
- Unexpected gear selection or failure to shift properly
- Possible transmission slippage or abnormal shift timing
What to check
- Read freeze-frame data and all stored transmission/engine codes with a scan tool
- Verify transmission fluid level and condition (low/dirty fluid can cause solenoid problems)
- Visually inspect solenoid connector, terminals, and wiring harness for damage or corrosion
- Backprobe the solenoid control connector and monitor voltage while commanding solenoid with a scan tool
- Measure solenoid coil resistance with connector disconnected
- Perform continuity checks to ground and to the TCM/PCM connector
Signal parameters
- Typical solenoid coil resistance (vehicle-specific): approximately 10-30 ohms (check service data)
- Expected control voltage range: ~0 V (ground) to ~12 V; control is often PWM-modulated
- PWM frequency: commonly 50–300 Hz (varies by vehicle and transmission)
- PWM duty cycle: 0–100% depending on commanded position/timing
- Typical steady-state current draw when energized: roughly 0.5–1.5 A (vehicle-specific)
Diagnostic algorithm
- Connect a professional scan tool. Record all transmission-related codes and freeze-frame. Note whether code is current or stored.
- Visually inspect the Shift Timing Solenoid A connector and nearby wiring for corrosion, melted insulation, pinched wires, or rodent damage.
- Check transmission fluid level and condition. Top or replace fluid if improper and retest; contaminated fluid can impair solenoid operation.
- With the engine off, disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Compare to factory spec. An open or very low resistance indicates a bad solenoid.
- Reconnect and backprobe the control and ground pins. With key on (engine running if safe) command the solenoid ON/OFF using the scan tool while monitoring voltage. A continuous high voltage or stuck-high when commanded off indicates a short to battery or driver fault.
- Check continuity from the solenoid control pin back to the TCM/PCM pin. Also verify a good ground path. Repair any opens or high-resistance connections.
- If short-to-voltage suspected, isolate sections of harness (disconnect intermediate connectors) to locate the short. Repair or replace damaged wiring or terminal.
- If wiring and connector check good and solenoid resistance is within spec but fault persists, consider swapping or bench-testing the solenoid (follow manufacturer safe bench-test procedure) or replacing the solenoid.
- If the solenoid and wiring are good, test or reflash the TCM/PCM as recommended by manufacturer. In rare cases the module driver is faulty and module replacement or repair is needed.
- After repairs, clear codes, perform functional tests/actuation with scan tool and complete a road test while monitoring shift timing and transmission parameters to confirm repair.
Likely causes
- Wire shorted to constant battery voltage at the solenoid connector
- Connector corrosion or pushed-out terminal producing poor contact
- Failed solenoid coil with internal short raising circuit voltage
- Open/poor ground upstream or at the control module
- Faulty TCM/PCM driver (less common than wiring/solenoid faults)
Fault status
Status
P0788 — Shift Timing Solenoid A High: control circuit voltage above expected threshold detected by TCM/PCM. Indicates electrical fault (short/high voltage), solenoid failure, or module driver issue.
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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Code
P0788
GWM
P — Powertrain
- High Solenoid Sensor Value
Views:
UK: 0
EN: 2
RU: 1
AI status
Completed
Completed
100%
Causes
- Short to battery/voltage in the solenoid control circuit
- Open or high-resistance ground in the solenoid circuit
- Failed shift timing solenoid (internal short or wiring fault)
- Damaged, corroded, or loose connector(s)
- Wiring chafing or pinched harness causing intermittent short
- Faulty TCM/PCM or poor driver transistor in control module
Symptoms
- Check Engine / Transmission warning light (MIL) illuminated
- Harsh, delayed, or erratic shifts
- Transmission may enter limp/reduced-gear mode
- Unexpected gear selection or failure to shift properly
- Possible transmission slippage or abnormal shift timing
What to check
- Read freeze-frame data and all stored transmission/engine codes with a scan tool
- Verify transmission fluid level and condition (low/dirty fluid can cause solenoid problems)
- Visually inspect solenoid connector, terminals, and wiring harness for damage or corrosion
- Backprobe the solenoid control connector and monitor voltage while commanding solenoid with a scan tool
- Measure solenoid coil resistance with connector disconnected
- Perform continuity checks to ground and to the TCM/PCM connector
Signal parameters
- Typical solenoid coil resistance (vehicle-specific): approximately 10-30 ohms (check service data)
- Expected control voltage range: ~0 V (ground) to ~12 V; control is often PWM-modulated
- PWM frequency: commonly 50–300 Hz (varies by vehicle and transmission)
- PWM duty cycle: 0–100% depending on commanded position/timing
- Typical steady-state current draw when energized: roughly 0.5–1.5 A (vehicle-specific)
Diagnostic algorithm
- Connect a professional scan tool. Record all transmission-related codes and freeze-frame. Note whether code is current or stored.
- Visually inspect the Shift Timing Solenoid A connector and nearby wiring for corrosion, melted insulation, pinched wires, or rodent damage.
- Check transmission fluid level and condition. Top or replace fluid if improper and retest; contaminated fluid can impair solenoid operation.
- With the engine off, disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Compare to factory spec. An open or very low resistance indicates a bad solenoid.
- Reconnect and backprobe the control and ground pins. With key on (engine running if safe) command the solenoid ON/OFF using the scan tool while monitoring voltage. A continuous high voltage or stuck-high when commanded off indicates a short to battery or driver fault.
- Check continuity from the solenoid control pin back to the TCM/PCM pin. Also verify a good ground path. Repair any opens or high-resistance connections.
- If short-to-voltage suspected, isolate sections of harness (disconnect intermediate connectors) to locate the short. Repair or replace damaged wiring or terminal.
- If wiring and connector check good and solenoid resistance is within spec but fault persists, consider swapping or bench-testing the solenoid (follow manufacturer safe bench-test procedure) or replacing the solenoid.
- If the solenoid and wiring are good, test or reflash the TCM/PCM as recommended by manufacturer. In rare cases the module driver is faulty and module replacement or repair is needed.
- After repairs, clear codes, perform functional tests/actuation with scan tool and complete a road test while monitoring shift timing and transmission parameters to confirm repair.
Likely causes
- Wire shorted to constant battery voltage at the solenoid connector
- Connector corrosion or pushed-out terminal producing poor contact
- Failed solenoid coil with internal short raising circuit voltage
- Open/poor ground upstream or at the control module
- Faulty TCM/PCM driver (less common than wiring/solenoid faults)
Fault status
Status
P0788 — Shift Timing Solenoid A High: control circuit voltage above expected threshold detected by TCM/PCM. Indicates electrical fault (short/high voltage), solenoid failure, or module driver issue.
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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Code
P0788
HUMMER
P — Powertrain
Shift/Timing Solenoid High
Views:
UK: 10
EN: 14
RU: 12
AI status
Completed
Completed
100%
Causes
- Short to battery/voltage in the solenoid control circuit
- Open or high-resistance ground in the solenoid circuit
- Failed shift timing solenoid (internal short or wiring fault)
- Damaged, corroded, or loose connector(s)
- Wiring chafing or pinched harness causing intermittent short
- Faulty TCM/PCM or poor driver transistor in control module
Symptoms
- Check Engine / Transmission warning light (MIL) illuminated
- Harsh, delayed, or erratic shifts
- Transmission may enter limp/reduced-gear mode
- Unexpected gear selection or failure to shift properly
- Possible transmission slippage or abnormal shift timing
What to check
- Read freeze-frame data and all stored transmission/engine codes with a scan tool
- Verify transmission fluid level and condition (low/dirty fluid can cause solenoid problems)
- Visually inspect solenoid connector, terminals, and wiring harness for damage or corrosion
- Backprobe the solenoid control connector and monitor voltage while commanding solenoid with a scan tool
- Measure solenoid coil resistance with connector disconnected
- Perform continuity checks to ground and to the TCM/PCM connector
Signal parameters
- Typical solenoid coil resistance (vehicle-specific): approximately 10-30 ohms (check service data)
- Expected control voltage range: ~0 V (ground) to ~12 V; control is often PWM-modulated
- PWM frequency: commonly 50–300 Hz (varies by vehicle and transmission)
- PWM duty cycle: 0–100% depending on commanded position/timing
- Typical steady-state current draw when energized: roughly 0.5–1.5 A (vehicle-specific)
Diagnostic algorithm
- Connect a professional scan tool. Record all transmission-related codes and freeze-frame. Note whether code is current or stored.
- Visually inspect the Shift Timing Solenoid A connector and nearby wiring for corrosion, melted insulation, pinched wires, or rodent damage.
- Check transmission fluid level and condition. Top or replace fluid if improper and retest; contaminated fluid can impair solenoid operation.
- With the engine off, disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Compare to factory spec. An open or very low resistance indicates a bad solenoid.
- Reconnect and backprobe the control and ground pins. With key on (engine running if safe) command the solenoid ON/OFF using the scan tool while monitoring voltage. A continuous high voltage or stuck-high when commanded off indicates a short to battery or driver fault.
- Check continuity from the solenoid control pin back to the TCM/PCM pin. Also verify a good ground path. Repair any opens or high-resistance connections.
- If short-to-voltage suspected, isolate sections of harness (disconnect intermediate connectors) to locate the short. Repair or replace damaged wiring or terminal.
- If wiring and connector check good and solenoid resistance is within spec but fault persists, consider swapping or bench-testing the solenoid (follow manufacturer safe bench-test procedure) or replacing the solenoid.
- If the solenoid and wiring are good, test or reflash the TCM/PCM as recommended by manufacturer. In rare cases the module driver is faulty and module replacement or repair is needed.
- After repairs, clear codes, perform functional tests/actuation with scan tool and complete a road test while monitoring shift timing and transmission parameters to confirm repair.
Likely causes
- Wire shorted to constant battery voltage at the solenoid connector
- Connector corrosion or pushed-out terminal producing poor contact
- Failed solenoid coil with internal short raising circuit voltage
- Open/poor ground upstream or at the control module
- Faulty TCM/PCM driver (less common than wiring/solenoid faults)
Fault status
Status
P0788 — Shift Timing Solenoid A High: control circuit voltage above expected threshold detected by TCM/PCM. Indicates electrical fault (short/high voltage), solenoid failure, or module driver issue.
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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Code
P0788
LAND ROVER
P — Powertrain
Shift/Timing Solenoid High
Views:
UK: 5
EN: 9
RU: 8
AI status
Completed
Completed
100%
Causes
- Short to battery/voltage in the solenoid control circuit
- Open or high-resistance ground in the solenoid circuit
- Failed shift timing solenoid (internal short or wiring fault)
- Damaged, corroded, or loose connector(s)
- Wiring chafing or pinched harness causing intermittent short
- Faulty TCM/PCM or poor driver transistor in control module
Symptoms
- Check Engine / Transmission warning light (MIL) illuminated
- Harsh, delayed, or erratic shifts
- Transmission may enter limp/reduced-gear mode
- Unexpected gear selection or failure to shift properly
- Possible transmission slippage or abnormal shift timing
What to check
- Read freeze-frame data and all stored transmission/engine codes with a scan tool
- Verify transmission fluid level and condition (low/dirty fluid can cause solenoid problems)
- Visually inspect solenoid connector, terminals, and wiring harness for damage or corrosion
- Backprobe the solenoid control connector and monitor voltage while commanding solenoid with a scan tool
- Measure solenoid coil resistance with connector disconnected
- Perform continuity checks to ground and to the TCM/PCM connector
Signal parameters
- Typical solenoid coil resistance (vehicle-specific): approximately 10-30 ohms (check service data)
- Expected control voltage range: ~0 V (ground) to ~12 V; control is often PWM-modulated
- PWM frequency: commonly 50–300 Hz (varies by vehicle and transmission)
- PWM duty cycle: 0–100% depending on commanded position/timing
- Typical steady-state current draw when energized: roughly 0.5–1.5 A (vehicle-specific)
Diagnostic algorithm
- Connect a professional scan tool. Record all transmission-related codes and freeze-frame. Note whether code is current or stored.
- Visually inspect the Shift Timing Solenoid A connector and nearby wiring for corrosion, melted insulation, pinched wires, or rodent damage.
- Check transmission fluid level and condition. Top or replace fluid if improper and retest; contaminated fluid can impair solenoid operation.
- With the engine off, disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Compare to factory spec. An open or very low resistance indicates a bad solenoid.
- Reconnect and backprobe the control and ground pins. With key on (engine running if safe) command the solenoid ON/OFF using the scan tool while monitoring voltage. A continuous high voltage or stuck-high when commanded off indicates a short to battery or driver fault.
- Check continuity from the solenoid control pin back to the TCM/PCM pin. Also verify a good ground path. Repair any opens or high-resistance connections.
- If short-to-voltage suspected, isolate sections of harness (disconnect intermediate connectors) to locate the short. Repair or replace damaged wiring or terminal.
- If wiring and connector check good and solenoid resistance is within spec but fault persists, consider swapping or bench-testing the solenoid (follow manufacturer safe bench-test procedure) or replacing the solenoid.
- If the solenoid and wiring are good, test or reflash the TCM/PCM as recommended by manufacturer. In rare cases the module driver is faulty and module replacement or repair is needed.
- After repairs, clear codes, perform functional tests/actuation with scan tool and complete a road test while monitoring shift timing and transmission parameters to confirm repair.
Likely causes
- Wire shorted to constant battery voltage at the solenoid connector
- Connector corrosion or pushed-out terminal producing poor contact
- Failed solenoid coil with internal short raising circuit voltage
- Open/poor ground upstream or at the control module
- Faulty TCM/PCM driver (less common than wiring/solenoid faults)
Fault status
Status
P0788 — Shift Timing Solenoid A High: control circuit voltage above expected threshold detected by TCM/PCM. Indicates electrical fault (short/high voltage), solenoid failure, or module driver issue.
Repair difficulty: Medium
Diagnostic time: 1-4 hours
Similar codes
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Code
P0788
MERCEDES-BENZ
P — Powertrain
Shift/Timing Solenoid High
Views:
UK: 9
EN: 12
RU: 14
AI status
Completed
Completed
100%
Causes
- Short to battery/voltage in the solenoid control circuit
- Open or high-resistance ground in the solenoid circuit
- Failed shift timing solenoid (internal short or wiring fault)
- Damaged, corroded, or loose connector(s)
- Wiring chafing or pinched harness causing intermittent short
- Faulty TCM/PCM or poor driver transistor in control module
Symptoms
- Check Engine / Transmission warning light (MIL) illuminated
- Harsh, delayed, or erratic shifts
- Transmission may enter limp/reduced-gear mode
- Unexpected gear selection or failure to shift properly
- Possible transmission slippage or abnormal shift timing
What to check
- Read freeze-frame data and all stored transmission/engine codes with a scan tool
- Verify transmission fluid level and condition (low/dirty fluid can cause solenoid problems)
- Visually inspect solenoid connector, terminals, and wiring harness for damage or corrosion
- Backprobe the solenoid control connector and monitor voltage while commanding solenoid with a scan tool
- Measure solenoid coil resistance with connector disconnected
- Perform continuity checks to ground and to the TCM/PCM connector
Signal parameters
- Typical solenoid coil resistance (vehicle-specific): approximately 10-30 ohms (check service data)
- Expected control voltage range: ~0 V (ground) to ~12 V; control is often PWM-modulated
- PWM frequency: commonly 50–300 Hz (varies by vehicle and transmission)
- PWM duty cycle: 0–100% depending on commanded position/timing
- Typical steady-state current draw when energized: roughly 0.5–1.5 A (vehicle-specific)
Diagnostic algorithm
- Connect a professional scan tool. Record all transmission-related codes and freeze-frame. Note whether code is current or stored.
- Visually inspect the Shift Timing Solenoid A connector and nearby wiring for corrosion, melted insulation, pinched wires, or rodent damage.
- Check transmission fluid level and condition. Top or replace fluid if improper and retest; contaminated fluid can impair solenoid operation.
- With the engine off, disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Compare to factory spec. An open or very low resistance indicates a bad solenoid.
- Reconnect and backprobe the control and ground pins. With key on (engine running if safe) command the solenoid ON/OFF using the scan tool while monitoring voltage. A continuous high voltage or stuck-high when commanded off indicates a short to battery or driver fault.
- Check continuity from the solenoid control pin back to the TCM/PCM pin. Also verify a good ground path. Repair any opens or high-resistance connections.
- If short-to-voltage suspected, isolate sections of harness (disconnect intermediate connectors) to locate the short. Repair or replace damaged wiring or terminal.
- If wiring and connector check good and solenoid resistance is within spec but fault persists, consider swapping or bench-testing the solenoid (follow manufacturer safe bench-test procedure) or replacing the solenoid.
- If the solenoid and wiring are good, test or reflash the TCM/PCM as recommended by manufacturer. In rare cases the module driver is faulty and module replacement or repair is needed.
- After repairs, clear codes, perform functional tests/actuation with scan tool and complete a road test while monitoring shift timing and transmission parameters to confirm repair.
Likely causes
- Wire shorted to constant battery voltage at the solenoid connector
- Connector corrosion or pushed-out terminal producing poor contact
- Failed solenoid coil with internal short raising circuit voltage
- Open/poor ground upstream or at the control module
- Faulty TCM/PCM driver (less common than wiring/solenoid faults)
Fault status
Status
P0788 — Shift Timing Solenoid A High: control circuit voltage above expected threshold detected by TCM/PCM. Indicates electrical fault (short/high voltage), solenoid failure, or module driver issue.
Repair difficulty: Medium
Diagnostic time: 1-4 hours
Similar codes
Your experience will help others
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Was this AI description helpful?
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Send to email