P0787 — Shift Timing Solenoid “A” Low #

The code description may differ depending on the vehicle manufacturer.

Common code label variations by manufacturer:

• Ford: Shift Timing Solenoid “A” Circuit Low
• GM (Chevrolet, GMC, etc.): Shift Solenoid “A” Performance – Low Control
• Toyota: Shift Solenoid “A” Low Voltage
• Honda: Shift Solenoid “A” Control Circuit Low
• Nissan: Shift Timing Solenoid “A” Function Low

Code summary for P0787 #

P0787 indicates a low voltage or low performance issue detected by the transmission control module (TCM) in the shift timing solenoid “A”. The solenoid is an electrically controlled valve responsible for managing hydraulic pressure and timing of gear shifts in automatic transmissions. The “low” state suggests the TCM is not receiving the expected electrical signal or shift response from solenoid “A” during operation. This can lead to problems with the timing or smoothness of gear changes, reduced fuel efficiency, or even transmission slippage. Addressing this code quickly is important to avoid further damage or expensive repairs.

Frequent symptoms for code P0787 #

When P0787 is active, you may notice several warning signs indicating transmission performance is compromised. Symptoms often start subtly but can worsen if ignored.

• Harsh or delayed gear shifts
• Transmission slipping or erratic shifting
• Failure to upshift or downshift
• Illuminated Check Engine Light (CEL)
• Reduced fuel efficiency
• Possible limp mode activation (vehicle stuck in a single gear)

Probable causes of code P0787 (by frequency) #

The most common causes for P0787 relate to either the solenoid itself or its control circuit. While some issues are straightforward, others may require deeper investigation.

1. Faulty shift timing solenoid “A” (electrical or mechanical failure)
2. Damaged, corroded, or loose solenoid wiring/connectors
3. Low, dirty, or contaminated transmission fluid
4. Malfunctioning transmission control module (TCM)
5. Internal transmission hydraulic problems
6. Blown fuse or relay associated with the solenoid circuit

Step-by-step diagnostic for P0787 #

A systematic approach ensures you pinpoint the root cause without overlooking simple issues. Always start with the basics before diving into complex repairs.

• 1. Verify the code with a reliable OBD-II/EOBD scanner and record freeze frame data.
• 2. Inspect transmission fluid level and condition; top up or replace if necessary.
• 3. Perform a visual inspection of wiring and connectors at solenoid “A” and the transmission harness.
• 4. Test solenoid “A” resistance with a multimeter (compare to OEM specifications).
• 5. Check for power and ground at the solenoid connector (key on, engine off/idle).
• 6. Inspect related fuses and relays for continuity and correct operation.
• 7. If wiring and solenoid test normal, evaluate the TCM for faults or perform OEM-specific software diagnosis.
• 8. If all else checks out, consider a transmission hydraulic pressure test or further mechanical inspection.

Possible repairs for P0787 #

Repair options depend on your findings. Always address the most probable and accessible cause first before considering major work.

• Replace faulty shift timing solenoid “A”
• Repair or replace damaged/loose wiring or connectors
• Replace or flush transmission fluid and filter
• Replace blown fuse or faulty relay
• Repair or replace transmission control module (TCM) (if proven faulty)
• Address internal transmission problems (if identified via pressure tests or teardown)

Can you drive with code P0787? #

Driving with P0787 is possible, but not recommended for extended periods. Mild symptoms like delayed shifting may be manageable in the short term, but continued operation can accelerate wear inside the transmission or leave you stranded in limp mode. If you notice severe symptoms—like harsh shifts, slippage, or failure to change gears—limit driving and seek diagnosis promptly to avoid permanent damage or costly repairs.

Vehicles most commonly affected by P0787 #

While P0787 is a generic OBD-II code, it is most frequently reported on vehicles using electronically controlled automatic transmissions from the late 1990s to today. Some makes and models are more prone due to specific solenoid designs or fluid sensitivity.

• Chevrolet Silverado / GMC Sierra (4L60E/4L80E transmissions)
• Ford F-150 / Explorer (4R70W/5R55 transmissions)
• Toyota Camry / Corolla (U-series transmissions)
• Honda Accord / Civic (early 2000s models)
• Nissan Altima / Maxima (RE4F04B/Jatco units)

Common mistakes and best practices for P0787 #

Rushing the diagnostic process or skipping basics can lead to unnecessary parts replacement and higher costs. Always verify before acting.

• Replacing the solenoid without checking wiring or fluid first
• Overlooking poor ground connections or corroded terminals
• Ignoring transmission fluid quality or level
• Neglecting to clear the code and retest after repairs
• Failing to use OEM diagnostic procedures when available

Quick FAQ for code P0787 #

The following answers address common concerns about P0787 for both drivers and technicians.

• Q: Will clearing the code fix my transmission problem?
  A: No. Clearing the code may turn off the warning light temporarily, but the underlying electrical or hydraulic issue must be resolved, otherwise the code will return.
• Q: Is a transmission fluid flush always required?
  A: Not always, but if the fluid is dirty or low, a flush or change is recommended. Proper fluid quality is crucial for solenoid and transmission health.
• Q: Do I need special tools to diagnose P0787?
  A: A basic OBD-II scanner, multimeter, and access to wiring diagrams are essential. Advanced diagnostics may require OEM scan tools or transmission pressure test equipment.