PCM/IDM Communication Error
The P1668 code indicates a communication failure between the Powertrain Control Module (PCM) and the Injector Driver Module (IDM). This typically occurs in diesel engines, especially Ford Power Stroke models. The IDM controls fuel injector operation, and loss of communication can cause drivability issues, including misfires, rough running, or no-start conditions. The error may stem from wiring faults, connector corrosion, or module failures.
01. Most Common Causes
- Faulty IDM (Injector Driver Module)
- Open or shorted wiring between PCM and IDM
- Corroded or loose connectors at PCM or IDM
- Failed PCM (less common)
02. Symptoms You Will Notice
- Engine misfire or rough idle
- Hard starting or no-start condition
- Check Engine Light illuminated
- Reduced engine power or stalling
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes to narrow down the issue.
Step 2: Visually inspect wiring and connectors between PCM and IDM for damage or corrosion.
Step 3: Test continuity and resistance in the communication circuits using a multimeter.
Step 4: Check IDM power and ground supplies; replace IDM if faulty.
Step 5: If all else passes, test or replace the PCM.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The vehicle may stall or lose power unexpectedly, posing a safety risk. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: wiring repairs $100-$300, IDM replacement $200-$600, PCM replacement $500-$1000.