P1683 PCM-IDM Serial Communication Failure
The P1683 code indicates a loss of serial communication between the Powertrain Control Module (PCM) and the Injector Driver Module (IDM) in Ford Power Stroke diesel engines. The IDM controls the high-pressure fuel injectors and relies on a dedicated communication bus to exchange timing and status data with the PCM. When this link is broken, the PCM cannot precisely command fuel injection, leading to hard starting, rough idle, or loss of power. Diagnosis should focus on wiring integrity, connector condition, and IDM power supply before replacing modules.
01. Most Common Causes
- Failed or damaged IDM
- Open, shorted, or high-resistance PCM-IDM communication bus wiring
- Corroded, oxidized, or damaged pins in the IDM harness connectors
- Internal PCM failure preventing communication with the IDM
- Electrical interference or poor ground in the communication circuit
- Low voltage or power supply failure to the IDM
02. Symptoms You Will Notice
- Engine cranks but does not start
- Rough idle or misfire
- Loss of power or hesitation under load
- Check Engine Light illuminated
03. Step-by-Step Diagnosis
Scan for additional codes and verify P1683 is present
Inspect IDM and PCM connectors for corrosion, bent pins, or damage
Check for battery voltage and ground at the IDM power and ground pins
Test the communication bus wiring for opens, shorts, and excessive resistance
If wiring and power are good, swap or test with a known-good IDM
If problem persists, test or replace the PCM
1. Frequently Asked Questions
Is it safe to drive?▼
No, driving with P1683 is not recommended. The vehicle may stall, lose power, or fail to restart, creating a safety hazard.
How much does it cost to fix?▼
Repair costs range from $100 for a wiring repair to $800 or more for IDM or PCM replacement, including diagnostics.