P0788 - Shift Timing Solenoid A Circuit High
The P0788 code indicates that the Powertrain Control Module (PCM) has detected a high voltage condition in the shift timing solenoid A circuit. This solenoid controls hydraulic pressure to engage and disengage clutches for gear shifts. A high voltage reading suggests a short to power, open circuit, or faulty solenoid, leading to improper transmission operation.
01. Most Common Causes
- Faulty shift timing solenoid A
- Short to power in solenoid circuit wiring
- Open or high resistance in solenoid circuit
- Damaged PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or erratic shifting
- Transmission stuck in gear or limp mode
- Decreased fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect wiring and connectors for damage, corrosion, or shorts.
Step 3: Test solenoid resistance with a multimeter (typically 10-30 ohms).
Step 4: Check for power and ground at solenoid connector with key on.
Step 5: If wiring and solenoid are good, test PCM output or replace PCM.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a high voltage solenoid code can cause transmission damage or sudden failure, leading to unsafe driving conditions.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150 for a solenoid replacement, plus diagnostic fees. Wiring repairs may cost more if extensive.