GMC Code P1238: Causes, Symptoms and Repair
1. Meaning of GMC Code P1238
The Engine Control Module (ECM) activates the appropriate fuel injector during the compression stroke of each cylinder. It controls the Fuel Injection Control Module (FICM) by grounding the control circuit via a solid-state driver.
The ECM monitors the driver’s status, and if an incorrect voltage is detected for the commanded state of an injector, a Diagnostic Trouble Code (DTC) will be generated, including:
- P1223, P1226, P1229, P1232, P1235, P1238, P1241 or P1244.
2. Possible Causes of GMC Code P1238
Common causes of this error code are:
- Faulty fuel injector 6
- Fuel injector 6 harness open or shorted
- Poor electrical connection in fuel injector 6 circuit
- Faulty Fuel Injection Control Module (FICM)
- Faulty Engine Control Module (ECM)
3. Possible Symptoms
A vehicle displaying code P1238 may exhibit the following symptoms:
- Illuminated check engine light (or “Service Engine Soon” warning light)
- Engine misfire
- Rough idle
4. How to Repair GMC Code P1238?
Here are the recommended steps to diagnose and repair this issue:
- Check the possible causes mentioned above.
- Visually inspect the wiring harness and connectors related to fuel injector 6.
- Look for damaged components and inspect the connector pins for any breakage, bending, or corrosion.
5. Technical Notes
- If a single injector control circuit DTC is stored, an open circuit or poor connection is likely the cause.
- If four injector control circuit DTCs are set, a short to ground should be suspected.
- The cylinder groups involved are:
- Group 1: Cylinders 2, 3, 5, 8
- Group 2: Cylinders 1, 4, 6, 7
- If more than 4 DTCs are stored, a short circuit in the fuel injector control circuit is the most likely cause.