P1202 Key Off Voltage Low
The P1202 code indicates that the powertrain control module (PCM) has detected a voltage below the expected threshold on the key-off voltage monitoring circuit. This circuit allows the PCM to check the status of certain sensors and actuators when the vehicle is off, ensuring system integrity before the next start. A low voltage condition suggests an abnormal drop in electrical supply to the monitored circuit, possibly due to excessive resistance, a short to ground, or an internal PCM failure.
01. Most Common Causes
- Faulty PCM power relay or associated circuit
- Excessive resistance or corrosion in PCM harness connectors
- Short to ground in the key-off circuit wiring
- Internal PCM failure
- Weak battery or poor ground connections
- Blown or damaged fuse in the PCM power supply circuit
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Possible hard starting or no-start condition
- Battery drain or electrical issues
03. Step-by-Step Diagnosis
Check battery voltage and condition; ensure terminals are clean and tight.
Inspect PCM power relay and fuses; replace if blown.
Visually inspect PCM harness connectors for corrosion, damage, or loose pins.
Test for voltage drop in the key-off circuit; repair any shorts or opens.
If all else fails, test or replace the PCM.
1. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but a low voltage condition can cause intermittent stalling or no-start. It's best to diagnose and repair promptly to avoid being stranded.
How much does it cost to fix?▼
Repair costs vary widely: simple fuse or relay replacement can be $20-$100; wiring repairs $100-$300; PCM replacement $500-$1000+ including programming.