Faulty shift/timing solenoid with an internal short or open winding; Damaged or corroded wiring harness or connector at the solenoid; Short to ground in the solenoid control circuit; Transmission control module (TCM) internal fault; Low transmission fluid level or contaminated fluid causing solenoid malfunction; Valve body issues that affect solenoid operation

DTC codes / P07xx · Transmission / P0787

P0787Shift/Timing Solenoid Low

Q: What does code P0787 mean?

Shift/Timing Solenoid Low. P0787 indicates that the transmission control module has detected an abnormally low current or voltage on the circuit for a shift/timing solenoid, which is responsible for controlling hydraulic pressure during gear changes. The computer sets this code when the solenoid's electrical signature falls outside the expected range, often due to a short to ground, a faulty solenoid, or wiring damage.

P0787 indicates that the transmission control module has detected an abnormally low current or voltage on the circuit for a shift/timing solenoid, which is responsible for controlling hydraulic pressure during gear changes. The computer sets this code when the solenoid's electrical signature falls outside the expected range, often due to a short to ground, a faulty solenoid, or wiring damage.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaTransmission

Symptoms you may notice

Illuminated check engine light or transmission warning light, often with no other noticeable symptoms
Harsh or delayed gear shifts, especially when the transmission is cold
Transmission may enter limp mode, limiting vehicle speed and gear selection
Slipping or flaring during upshifts or downshifts
In some cases, the transmission may not shift at all or may stay in a single gear

Common causes, most likely first

Faulty shift/timing solenoid with an internal short or open winding
Damaged or corroded wiring harness or connector at the solenoid
Short to ground in the solenoid control circuit
Transmission control module (TCM) internal fault
Low transmission fluid level or contaminated fluid causing solenoid malfunction
Valve body issues that affect solenoid operation

How to diagnose and fix it

Check transmission fluid level and condition; top off or replace fluid if necessary
Inspect the solenoid wiring harness and connectors for damage, corrosion, or loose pins
Measure the resistance of the shift/timing solenoid and compare to manufacturer specifications
Test the solenoid control circuit for a short to ground using a multimeter
If the solenoid is faulty, replace it and clear the code
If wiring is damaged, repair or replace the affected section of the harness
If the TCM is suspected, perform a diagnostic check with a scan tool capable of bidirectional controls and follow manufacturer troubleshooting steps

Don't overlook the wiring harness

A common oversight is replacing the solenoid without checking the wiring harness for chafed or melted insulation, which can cause a short to ground and set P0787.
This code can be set by a low transmission fluid level that causes the solenoid to overheat and fail, so always check fluid condition before condemning the solenoid.
Some vehicles use a single solenoid for multiple shift functions, so a failure may cause symptoms in more than one gear, leading to misdiagnosis of a mechanical transmission problem.
A faulty TCM can mimic a solenoid circuit fault, so perform a thorough circuit test before replacing the TCM, as it is often the most expensive part.
P0787 may be accompanied by other solenoid codes if the shared power or ground circuit is compromised, so inspect the entire circuit rather than just the solenoid.

Can I keep driving with P0787?

It is generally safe to drive short distances to a repair shop, but avoid heavy acceleration or towing, as the transmission may enter limp mode or shift erratically, increasing the risk of further damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.