Fix P0690: Mechanic’s solutions that WORKED

The OBD2 code P0690 indicates a problem with the Engine Control Module (ECM) Power Relay Sense Circuit, specifically that the signal is too high. This relay is critical for supplying power to the ECM, which in turn controls the engine and various other vehicle functions. When this circuit malfunctions, it can lead to issues such as engine hesitation, poor acceleration, or even prevent the engine from starting.

P0690 quick overview

Meaning	P0690: ECM Power Relay Sense Circuit High
Is it serious?	Yes, because it can affect the vehicle’s starting capability and overall performance.
Possible causes	– Faulty ECM power relay – Wiring issues in the relay circuit – Poor relay ground connection – ECM fault
How to diagnose?	Inspect the ECM power relay and its connections for damage or corrosion Check the relay circuit wiring for shorts or open circuits Test the relay ground connection for continuity Evaluate the ECM for potential issues affecting the relay circuit

How to fix P0690 – learn from mechanics

I looked into P0690 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Chevrolet

Vehicle Information 2010 Chevrolet Equinox LS 2.4L

Issue + Repair History

• Customer complaint of engine hesitation and poor acceleration, especially when cold.
• Symptoms include intermittent stalling at idle and loss of power during initial acceleration.
• OBD2 trouble codes present: P0690 (Engine controls relay feedback circuit high), P2119 (Throttle Closed Position Performance).
• Previous repair attempts include replacing the throttle body, carbon cleaning, and repairing a collapsed vacuum hose.

Other OBD2 Codes + Test Results

• P0690: Engine controls relay feedback circuit high
• P2119: Throttle Closed Position Performance

Mechanic Suggestions

• Replace the ECM relay and inspect the TAC ground for voltage issues.
• Check coil boots and spark plugs for carbon tracking, perform a crank relearn, and inspect for vacuum leaks.
• Consider reprogramming the PCM to address the false P0690 code (TSB #PIT5065C).
• Monitor intake and exhaust cam positions for discrepancies that could indicate camshaft issues.
• Investigate the high-pressure fuel pump for potential leaks or malfunction.

Final Fix

• Discovered a problem with the O2 sensor after consulting a GM bulletin specific to 2010 Equinox models with similar symptoms.
• Replaced the O2 sensor, resolving the issue of engine hesitation and intermittent stalling.
• Confirmed that all fault codes were cleared and engine performance returned to normal.

Case #2: Chevrolet

Vehicle Information 2010 Chevrolet Silverado 2500 HD LT 6.0L

Issue + Repair History

• Customer complaint of MIL (Malfunction Indicator Lamp) illuminated.
• OBD2 trouble codes present: P0106 (MAP/Baro sensor range performance), P0107 (MAP or Baro circuit low input), P0453 (Evap system pressure sensor/switch high input), P0523 (EOP sensor high input), P0461 (Sensor reference voltage A circuit open), P0690 (ECM/PCM power relay sense high circuit).
• Initial diagnostics revealed that the 5V reference bus 1 has a constant voltage of 12V.
• Unplugging various sensors did not resolve the issue.
• Removal of the PCM power relay restored the 5V reference to normal levels.

Other OBD2 Codes + Test Results

• P0106: MAP/Baro sensor range performance
• P0107: MAP or Baro circuit low input
• P0453: Evap system pressure sensor/switch high input
• P0523: EOP sensor high input
• P0461: Sensor reference voltage A circuit open
• P0690: ECM/PCM power relay sense high circuit

Mechanic Suggestions

• Check 5V reference voltage directly at the PCM with all sensor 5V feed wires disconnected at PCM side.
• Test the load side of the PCM relay circuit for a short to reference voltage.
• Verify that all PCM grounds can handle amperage without voltage drop.
• Ensure that the PCM ignition supply is not shorted to the 5V reference circuit.
• Verify the correct disconnection of the Fuel Tank Pressure sensor and inspect for moisture or corrosion at the X300 connector next to the transmission.

Final Fix

• Discovered a short in the wiring harness, specifically with the 5V reference wires being shorted to the two pink wires off the fuse for the upstream O2 sensors.
• Repaired the shorted wiring harness and verified the repair by running an overlay to confirm that the 5V reference returned to normal levels.
• Customer informed of the issue and the option to replace the harness if desired.

Case #3: Ford

Vehicle Information 2006 Ford Fusion SE 2.3L

Issue + Repair History

• Customer reported issues with a dead battery and erratic instrument cluster behavior.
• Replaced battery, but problem persisted.
• A year later, the dead battery issue escalated to a no-crank, no-start condition.
• Upon inspection, observed no dash lights except for a blinking Air Bag light and twitching gauges.
• Intermittently, the dash would briefly display a bulb check but then revert to no response.
• Click noise heard behind the dash when IGN is turned to start, indicating the switch is functional.
• PATS code P1260 persisted after clearing codes, still no crank.
• Limited diagnostic capabilities through OTC Genysis scanner.
• Suspected power draw issue leading to dead battery.

Other OBD2 Codes + Test Results

• P0462: Fuel level circuit low input
• P0690: ECM/PCM power relay sense circuit high
• P1260: Theft detected engine disable
• P2072: Throttle actuator control system – Ice Blockage

Mechanic Suggestions

• Try starting with a different key to rule out key-related issues.
• Check ignition switch powers to ensure power is reaching and leaving the switch when energized.
• Verify power distribution from the switch to the PCM, checking for shorts or poor connections.
• Inspect cooling fan wiring for potential over-amping and melted wiring.

Final Fix

• The vehicle was sent to the dealer, where the instrument cluster was replaced.
• No further details provided regarding resolution of the no-crank, no-start condition.

Diagnostic Step	Explanation
Inspect the ECM power relay and connections	Look for any visible signs of damage, corrosion, or loose connections.
Check the relay circuit wiring	Examine for shorts, open circuits, or damaged insulation that could cause high readings.
Test the relay ground connection	Ensure the ground connection is secure and has good continuity.
Evaluate the ECM	Check for any signs of damage or malfunction that could affect relay operation.
Replace the ECM relay	If the relay is found to be faulty, replacing it may resolve the issue.
Reprogram the PCM if applicable	Follow manufacturer TSBs for software updates that address the false P0690 code.
Inspect and repair wiring harness if necessary	Look for and repair any shorts or damage in the wiring harness affecting the 5V reference circuit.
Check other related systems and sensors	Examine related sensors and circuits that could contribute to the issue, such as the O2 sensor or fuel pressure system.

Addressing a P0690 code requires a comprehensive approach to diagnose and fix the electrical issues within the ECM power relay circuit. Always consult with a professional mechanic to ensure accurate diagnostics and repairs, especially for complex electrical system problems.