Ignition Switch Invalid Voltage Code
The body control module (BCM) or powertrain control module (PCM) has detected an invalid combination of voltages on the ignition switch input circuits. The ignition switch uses multiple signal circuits to encode the key position (Off, Acc, Run, Start). This code is set when the reading from these circuits does not match any predefined valid position, indicating a failure in position encoding.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty or worn ignition switch internal contacts
- Short to ground, short to battery, or open circuit in the wiring between the ignition switch and BCM/PCM
- Damaged, corroded, or loose terminals in ignition switch or BCM/PCM connectors
- Internal failure of the BCM or PCM
- Aftermarket accessories (remote start, alarms) interfering with ignition switch signals
- Mechanical wear of the lock cylinder preventing proper contact of switch tracks
3. Symptoms You Will Notice
- Engine may not start or stalls unexpectedly
- Dashboard lights or accessories behave erratically or fail to respond to key position
4. Step-by-Step Diagnosis
Check for technical service bulletins (TSBs) related to the ignition switch or BCM/PCM for the specific vehicle.
Inspect the ignition switch connector and BCM/PCM connectors for damage, corrosion, or loose pins.
Test the ignition switch signal circuits for shorts, opens, or correct voltage patterns using a multimeter.
If wiring and connectors are okay, replace the ignition switch and re-evaluate.
If the code persists, test the BCM/PCM for internal faults or consider reprogramming.
5. Frequently Asked Questions
Is it safe to drive?▼
No, this is a high-severity issue. The vehicle may stall or fail to start unexpectedly, posing a safety risk. It is recommended to have the vehicle towed to a repair shop.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on the root cause. Ignition switch replacement is usually $150-$300, while BCM/PCM replacement can exceed $500.