P1358
FordIDM Signal Out Of Self Test Range (No CPUOK)
The PCM did not receive the expected CPUOK status signal from the Injector Driver Module (IDM) during a self-test. The IDM helps control injector operation; this code reports a missing or out-of-range status response, not proof that the IDM itself has failed. Depending on the vehicle and fault, the engine may run poorly or may not start.
⚠️ Before You Begin (Safety First)
If the engine stalls, will not start reliably, or loses power in traffic, stop driving and arrange appropriate service. Do not probe energized IDM or injector circuits; these systems can involve hazardous voltages. Exact precautions depend on the vehicle and engine.
Common Symptoms
- The check-engine light may be on because the PCM recorded a failed IDM self-test response.
- The engine may crank without starting if the IDM status problem interferes with injector operation.
- Rough running, reduced power, or stalling may occur if the IDM or its signal circuit is intermittently affected.
- There may be no noticeable symptoms if the code is intermittent or the engine continues to operate normally.
Common Causes
- A damaged, loose, corroded, or poorly connected IDM connector or wiring may interrupt the CPUOK signal.
- A fault in IDM power or ground connections may prevent the module from reporting its status correctly.
- An open, short, or other wiring fault in the CPUOK signal path may prevent the PCM from receiving the expected response.
- The IDM may have an internal fault, but this code alone does not establish that the module needs replacement.
- A fault in the PCM or its connection to the signal circuit is possible after other causes are checked.
Diagnostic Steps
- Record the code and note whether the engine starts, runs poorly, or stalls; these details help distinguish an intermittent status signal from a persistent operating problem.
- With the ignition off, visually inspect accessible IDM connectors and wiring for looseness, corrosion, chafing, or obvious damage. Do not disconnect or handle components contrary to the vehicle-specific safety instructions.
- Check that the battery connections are secure and free of obvious corrosion, since poor electrical connections can affect module operation.
- If the code returns, avoid replacing the IDM based on the code alone. Have the CPUOK circuit and IDM power and ground tested using the correct wiring information and safe test equipment.
When to Call a Professional
Confirm the code and check for related codes and relevant scan data. Use the vehicle-specific wiring information to inspect and test IDM power, ground, connectors, and the CPUOK signal path. Check for wiring damage or poor connections before condemning the IDM or PCM. Follow the model-specific procedure and use equipment suitable for the circuit.
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Commonly Asked Questions
Does P1358 prove that the IDM is bad?
No. It means the PCM did not receive the expected CPUOK status during a self-test. Wiring, connectors, power, ground, or the signal path can cause the same detected condition.
What does CPUOK refer to here?
It is the IDM status signal expected by the PCM during the self-test. The code indicates that the response was missing or outside the expected range; it does not identify the failed part by itself.
Can the vehicle still run with this code?
Possibly. Some vehicles may have no obvious symptoms, while others may run poorly, lose power, stall, or fail to start. Behavior depends on the vehicle and the fault.
Should I replace the IDM first?
No. Check the relevant connections, power, ground, and CPUOK signal path first. The applicable test procedure depends on the vehicle's model, year, and engine.
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