P0787: Shift Timing Solenoid A Low
The P0787 code indicates that the Powertrain Control Module (PCM) has detected a low voltage or resistance condition in the shift timing solenoid A circuit. This solenoid controls hydraulic pressure to engage specific gears in the automatic transmission. A low signal suggests a short to ground, open circuit, or faulty solenoid, leading to improper shift timing and potential transmission damage.
01. Most Common Causes
- Faulty shift timing solenoid A
- Wiring or connector issues (short to ground, open circuit)
- Low transmission fluid level or dirty fluid
- Internal transmission mechanical failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifts
- Transmission slipping or stuck in gear
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Check transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually inspect wiring and connectors for damage, corrosion, or loose connections.
Step 4: Test solenoid A resistance with a multimeter (specs vary by vehicle; typically 10-30 ohms).
Step 5: If solenoid is faulty, replace it; if wiring is bad, repair or replace harness.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as low solenoid voltage can cause harsh shifting, transmission slipping, or internal damage. Seek repair promptly.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150 for a solenoid replacement if DIY, or $200-$400 at a shop including labor and diagnostics.