P1502: Invalid Test APCM Functioning
The P1502 code indicates that the Auxiliary Powertrain Control Module (APCM) has detected an invalid test result during its self-check routine. This typically points to a communication or internal fault within the APCM, which may affect vehicle systems like the alternator, battery management, or auxiliary power functions. The APCM is responsible for managing non-engine electrical loads, and a malfunction can lead to charging system issues or erratic electrical behavior.
01. Most Common Causes
- Faulty Auxiliary Powertrain Control Module (APCM)
- Corroded or damaged wiring/connectors to the APCM
- Low battery voltage or poor ground connection
- Software glitch or outdated APCM firmware
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Battery warning light on dashboard
- Electrical accessories malfunctioning (e.g., power windows, radio)
- Vehicle may enter limp mode or have reduced power
03. Step-by-Step Diagnosis
Step 1: Scan the vehicle with an OBD2 scanner to confirm P1502 and check for other codes.
Step 2: Inspect the APCM wiring and connectors for corrosion, damage, or loose connections.
Step 3: Test battery voltage and charging system output; ensure battery is fully charged.
Step 4: Perform a APCM self-test using a professional scan tool to verify module functionality.
Step 5: If all else fails, replace the APCM and reprogram it with the latest software.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with P1502, as it can cause unexpected electrical failures or battery drain. You may be able to drive to a repair shop, but be prepared for potential stalling or loss of power.
How much does it cost to fix?▼
The cost to fix P1502 typically ranges from $150 to $400, including diagnostic time and parts. If the APCM needs replacement, parts alone can cost $100-$300, plus labor.