Shift Solenoid Control Circuit Range/Performance
The P099A code indicates that the transmission control module (TCM) has detected a range or performance issue in the control circuit of a shift solenoid. This typically means the solenoid's electrical circuit is out of expected parameters, possibly due to high resistance, a short, or a faulty solenoid. The TCM monitors the solenoid's response and sets this code when the actual current or voltage does not match the commanded value, affecting transmission shifting behavior.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifting
- Transmission stuck in gear or limp mode
- Decreased fuel economy
2. Most Common Causes
- Faulty shift solenoid 'G' or altered internal resistance
- Solenoid circuit wiring shorted to ground, shorted to voltage, or open
- Corroded, loose, or moisture-damaged solenoid connector or terminals
- Internal failure of the transmission control module (TCM)
- Poor transmission fluid level or condition (low level, worn, or contaminated)
- Mechanical blockage in the transmission valve body affecting solenoid operation
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect transmission fluid level and condition.
Step 3: Visually check wiring and connectors for damage or corrosion.
Step 4: Test the shift solenoid resistance and power/ground circuits with a multimeter.
Step 5: Perform a solenoid actuation test using a scan tool if available.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause erratic shifting or transmission damage. Limp mode may limit speed, but you should have it diagnosed promptly.
How much does it cost to fix?▼
The cost typically ranges from $150 to $400, including parts and labor. A shift solenoid replacement is often $50-$150 for the part, plus labor for diagnosis and installation.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.