The P0689: ECM/PCM Power Relay Sense Circuit Low code indicates that the control module has detected a lower-than-expected voltage in the power relay sense circuit for the ECM (Engine Control Module) or PCM (Powertrain Control Module). This may result in improper operation of the control module, affecting engine performance or causing starting issues. Low voltage in this circuit could be due to a faulty relay, wiring problems, or a malfunction in the circuit.
P0689 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P0689: ECM/PCM Power Relay Sense Circuit Low |
| Is it serious? | Yes, as it can lead to improper ECM/PCM operation and potential engine starting problems. |
| Possible causes | – Low voltage in ECM/PCM power relay sense circuit – Faulty relay – Wiring issue |
| How to diagnose? | – Test ECM/PCM power relay sense circuit for voltage – Inspect wiring and connectors – Replace relay if necessary |
P0689 Meaning
The P0689 code indicates that the voltage in the power relay sense circuit for the ECM/PCM is lower than the expected range. This sense circuit monitors the operation of the power relay, ensuring that it provides the necessary voltage for the ECM/PCM to function. Low voltage can cause the ECM/PCM to malfunction, leading to poor engine performance or starting issues.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for additional codes related to the ECM, PCM, or power relay system to gather more information about the problem. | OBD-II Scanner |
| Test the ECM/PCM Power Relay Sense Circuit for Voltage | Use a multimeter to measure the voltage in the ECM/PCM power relay sense circuit. Verify the voltage readings against manufacturer specifications. | Multimeter |
| Inspect Wiring and Connectors | Inspect the wiring and connectors leading to the ECM/PCM power relay for any signs of damage, corrosion, or loose connections that could cause low voltage. | Flashlight, Multimeter |
| Test the Power Relay | Test the power relay for proper operation. If the relay is faulty and not providing the correct voltage to the ECM/PCM, replace it. | Diagnostic Tool, Multimeter |
| Replace the Relay if Necessary | If the power relay is found to be defective and causing the low voltage, replace it to restore proper function to the ECM/PCM. | Replacement Relay, Tools |
| Clear the Code and Test | After repairs, clear the code using an OBD-II scanner and test the vehicle to ensure the ECM/PCM power relay sense circuit is functioning correctly. | OBD-II Scanner, Vehicle Manual |
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I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko