Shift Timing Solenoid A Circuit High
The P0788 code indicates that the Powertrain Control Module (PCM) has detected a high voltage or resistance in the electrical circuit of Shift Timing Solenoid A. This solenoid controls hydraulic pressure to adjust shift timing in the automatic transmission. A high signal suggests an open circuit, short to power, or faulty solenoid, leading to erratic shifting or transmission slippage.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifts
- Transmission stuck in gear or limp mode
- Poor fuel economy
- Transmission slipping
2. Most Common Causes
- Short to voltage in the solenoid circuit wiring
- Shift/timing solenoid damaged or internal resistance out of range
- Solenoid connector corroded, bent, or with damaged pins
- Faulty transmission control module (TCM) or PCM
- Transmission harness wiring damaged (chafing or extreme heat)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually check wiring and connectors for damage, corrosion, or loose connections.
Step 4: Test solenoid resistance with a multimeter; compare to manufacturer specs (typically 20-30 ohms).
Step 5: Check for power and ground at solenoid connector with key on; repair open/shorts as needed.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the transmission may shift erratically or fail, potentially causing a safety hazard. Limp mode may limit speed.
How much does it cost to fix?▼
Repair costs vary: DIY solenoid replacement can be $50-$150 for parts; professional labor adds $100-$200. If internal damage is found, costs can exceed $1000.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.