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.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifts
- Transmission slipping or stuck in gear
- Reduced fuel economy
2. 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
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect transmission fluid level and condition; top up or replace if necessary.
Step 3: Visually check wiring and connectors to solenoid A for damage, corrosion, or loose connections.
Step 4: Use a multimeter to test solenoid resistance (typically 10-30 ohms) and compare to specs.
Step 5: If wiring and solenoid are okay, test PCM output signals; replace PCM if faulty.
4. 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 erratic shifting, overheating, and potential transmission failure. Drive only to a repair shop.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150 for solenoid replacement, plus diagnostic fees. If internal transmission damage is found, costs can exceed $1,000.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.