P0690 — ECM/PCM Power Relay Sense Circuit High
P0690 is the standardized powertrain DTC for “ECM/PCM Power Relay Sense Circuit High.” The code identifies the monitored condition; it does not by itself prove which part failed.
What P0690 means
P0690 is the standardized powertrain DTC for “ECM/PCM Power Relay Sense Circuit High.” The code identifies the monitored condition; it does not by itself prove which part failed.
How to interpret the code wording
“Circuit High” means the module saw voltage or a signal above its calibrated range. Depending on circuit design, test for a short to voltage, an open/poor ground, an open signal circuit, terminal problems, or a failed sensor/actuator. Use the OEM wiring diagram because “high” does not identify the failed part by itself.
Possible symptoms
- Multiple warning lights
- Intermittent no-start or limp mode
- Communication loss
- Unexpected module behavior
Causes to test
These are diagnostic possibilities, not a statistical parts-replacement ranking. Vehicle-specific service information takes priority.
- Low/unstable system voltage
- Power/ground or connector problem
- CAN/network wiring fault
- Incorrect or incomplete programming/calibration
- Internal module fault
Step-by-step diagnostic workflow
- Stabilize and test battery/charging voltage before module replacement.
- Perform a full-vehicle module scan and identify which modules communicate.
- Check module power, grounds, fuses, and network termination/wiring.
- Review programming/calibration status and applicable service information.
- Replace/reprogram a module only after external causes are ruled out.
- Clear codes only after repair, then complete an appropriate drive cycle and verify the code and symptoms do not return.
Scan data worth checking
- Full module scan
- System voltage
- Network DTCs
- Module software/calibration identifiers where supported
Severity and drivability
Moderate to high depending on symptoms. Module codes are often secondary to voltage, network, connector, or calibration problems.
Stop driving and investigate immediately if there is a flashing MIL, oil-pressure warning, overheating, fuel leakage, severe misfire, major loss of power, abnormal mechanical noise, or a transmission that is slipping badly.
Common diagnostic mistakes
- Replacing a PCM/TCM based on a single internal code without power/ground checks
- Ignoring low-voltage history
- Programming a module without a stable power supply
Related generic codes
Source and accuracy notes
Generic DTC structure and standardized definitions are governed by SAE J2012/J2012DA. Actual enable criteria, thresholds, circuit pinouts, test values, software conditions, and repair procedures vary by vehicle. Use current OEM service information for the exact year/engine/calibration and check applicable manufacturer technical service bulletins. See the site methodology and primary-reference policy.