P0690 – ECM/PCM Power Relay Sense Circuit High

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: Circuit High

Definition source: SAE J2012/J2012DA (industry standard)

P0690 indicates the ECM/PCM has detected a “high” electrical condition on the power relay sense circuit it uses to verify relay command and/or feedback status. In practical terms, the module expected the sense signal to be at one state, but the circuit was seen higher than expected, which commonly points to a short-to-power, an open ground/return, a wiring fault, or an internal relay/contact issue that causes the sense line to remain elevated. How the sense circuit is routed and how the monitor runs varies by vehicle, so confirm the exact circuit design, connector pinouts, and test conditions using the correct service information before making conclusions or replacing parts.

What Does P0690 Mean?

P0690 – ECM/PCM Power Relay Sense Circuit High means the powertrain control module has identified a high-input condition in the circuit used to sense (confirm) the ECM/PCM power relay’s status. SAE J2012 defines the DTC structure, and for this code the fault type is specifically “Circuit High,” indicating the observed electrical signal on the sense line is higher than expected for the current operating state. The code does not, by itself, prove the relay or control module has failed; it reports an electrical condition in the relay sense circuit that must be verified with circuit testing.

Quick Reference

• Subsystem: ECM/PCM power relay sense (feedback) circuit and related power/ground paths.
• Common triggers: Sense circuit stuck high, short-to-power on the sense wire, open ground/return, miswired connector, or relay/contact behavior that keeps feedback high.
• Likely root-cause buckets: Wiring/connector faults, relay faults, power/ground distribution issues, or less commonly ECM/PCM driver/sense input concerns.
• Severity: Potentially high; may cause intermittent no-start, stalling, or loss of module power depending on vehicle strategy.
• First checks: Verify battery/charging stability, inspect relay and fuse/relay box terminals, check for corrosion/loose pins, and confirm grounds are intact.
• Common mistakes: Replacing the ECM/PCM or relay without testing the sense circuit for short-to-power or an open ground/return.

Theory of Operation

The ECM/PCM power relay supplies operating voltage to one or more module power feeds. Many designs also provide a sense (feedback) circuit so the ECM/PCM can confirm whether relay output is actually present when commanded, and absent when not commanded. The sense input may monitor relay output directly, a dedicated feedback contact, or a related power distribution point; the exact routing varies by vehicle.

P0690 sets when the ECM/PCM detects that the sense circuit remains electrically high when it should not be, or is higher than expected relative to the commanded relay state. This can occur if the sense wire is shorted to a power source, if the circuit’s return path is open so the input floats high, if relay contacts stick, or if connector/terminal conditions create unintended continuity to power.

Symptoms

• No-start: Engine may crank without starting if the module power state is not being managed correctly.
• Stall: Intermittent engine stall, especially during key transitions or vibration-related events.
• Intermittent power loss: Dash indicators or module communications may reset if module power is unstable.
• Extended crank: Longer-than-normal crank time if power relay control/verification delays enablement.
• Warning lamp: Malfunction indicator lamp illuminated with stored or pending P0690.
• Reduced performance: Some vehicles may enter a protective mode if module power integrity cannot be verified.

Common Causes

• Short-to-power on the ECM/PCM power relay sense circuit (rubbed-through insulation contacting a voltage feed)
• High resistance or open on the sense circuit’s ground/return path causing the sensed signal to remain high
• Connector issues at the relay, fuse/relay center, or ECM/PCM (backed-out terminals, corrosion, poor pin fit, moisture intrusion)
• Incorrect relay installed or relay with internal leakage/stuck contacts that biases the sense line high
• Fault in the relay control circuit wiring that backfeeds the sense circuit (misrouted harness or shared splices)
• Fuse/relay center internal faults (damaged bus bar, overheated cavity, or cross-feed between adjacent circuits)
• Aftermarket or add-on electrical equipment causing backfeed into the ignition/relay sense circuits (installation-dependent)
• ECM/PCM internal input fault on the power relay sense circuit (less common; confirm all external circuits first)

Diagnosis Steps

Tools typically needed include a scan tool capable of reading DTCs, freeze-frame, and live data; a digital multimeter; basic back-probing leads; and service information with wiring diagrams and connector views (pinouts vary by vehicle). A test light and tools for connector inspection/terminal tension checks can help, and a battery charger is recommended to keep system voltage stable during testing.

1. Confirm the complaint and capture data: Scan for DTCs and record freeze-frame and all pending/history codes. Note any power supply, ignition, or relay-related codes that could change the diagnostic path. Clear codes only after data is saved.
2. Verify the condition is repeatable: Cycle the ignition and perform a short road test or key-on run (as applicable) while monitoring the ECM/PCM power relay sense parameter(s) in live data (names vary by vehicle). Confirm the monitor returns and is reported as “high.”
3. Check battery and primary power integrity first: Inspect battery terminals for looseness/corrosion and confirm main power and ground connections are secure. If the vehicle shows unstable electrical behavior (multiple modules resetting, flickering lamps), address that before focusing on the sense circuit.
4. Inspect fuses/relay center and relay fitment: Verify correct relay type/part for the cavity (varies by vehicle) and that the relay seats fully. Inspect the relay cavity for heat damage, spread terminals, or contamination. Swap with a known-good same-type relay only as a test, then retest for code return.
5. Visual harness/connector inspection: Inspect the wiring from the fuse/relay center to the ECM/PCM for chafing, pinch points, recent repairs, or add-on equipment taps. Pay close attention to areas near sharp brackets and harness bends. Repair obvious damage and then recheck.
6. Wiggle test with live data logging: With the scan tool logging the power relay sense input, gently wiggle the relay, relay-center connectors, and harness sections leading to the ECM/PCM. If the sense reading drops/changes or the engine stumbles, isolate the section that reacts and focus inspection there.
7. Check for unwanted voltage on the sense circuit: Using the wiring diagram, identify the ECM/PCM power relay sense pin and back-probe it. With ignition states as specified by service info, verify whether the sense circuit shows an abnormally high electrical state when it should not. If it stays high, suspect a short-to-power or backfeed.
8. Isolate backfeed by unplugging components one at a time: If the sense remains high, disconnect the relay (and, if applicable, relevant fuse/relay center connectors) and recheck the sense circuit. If the high condition disappears when a connector is unplugged, the fault is likely downstream of that point (relay-center internal cross-feed, connector contamination, or harness short).
9. Continuity and short-to-power checks (key off): With power safely removed per service info, check the sense circuit for continuity end-to-end and for shorts to power feeds. A short to a power supply or shared splice can hold the sense line high. Repair wiring faults found and verify terminal integrity.
10. Voltage-drop testing of power and ground paths: If the circuit checks good but the issue persists under load, perform voltage-drop tests on the ECM/PCM power feed and grounds related to the power relay circuit (exact points vary by vehicle). Excessive drop or poor ground can create abnormal sensed states and intermittent resets; correct connection/ground issues before considering module faults.
11. Verify repair with a complete drive cycle: After repairs, clear DTCs, then run the conditions required for the monitor (varies by vehicle). Confirm the sense input behaves normally in live data and that P0690 does not return as pending or confirmed.

Professional tip: Treat “circuit high” as an electrical diagnosis: prioritize finding a short-to-power, backfeed, or a lost ground/return that prevents the sense line from being pulled to the expected state. If you suspect an intermittent harness or relay-center issue, keep a live-data log running during a wiggle test and heat/vibration exposure; a single captured transition often pinpoints the exact connector or splice to open up and inspect.

Possible Fixes & Repair Costs

Repair cost for P0690 varies widely because the root cause can be anything from a simple connection issue to relay control or module power-feed faults. Total expense depends on confirmed diagnosis results, parts replacement needs, and labor time based on access and wiring complexity.

• Clean, reseat, and secure connectors related to the ECM/PCM power relay and its sense circuit; repair any bent, backed-out, or loose terminals found during inspection.
• Repair wiring faults in the power relay sense circuit (short-to-power, chafed insulation, poor splices) and restore proper routing/retention to prevent repeat damage.
• Restore ECM/PCM power and ground integrity by correcting high-resistance connections (corrosion, loose fasteners) and repairing damaged ground points or power feeds verified by testing.
• Replace the ECM/PCM power relay if relay function or internal contact integrity fails testing and the sense circuit is confirmed to be reading high due to relay-related behavior.
• Repair or replace the relay control circuit components (as applicable, varies by vehicle) if testing proves the relay is being driven incorrectly or the feedback path is shorted to power.
• Update/reprogram control module software only if service information indicates it applies and all power/ground/sense circuit checks pass; otherwise avoid software as a first step.
• Replace the ECM/PCM only after verifying correct power/ground feeds, correct relay operation, and correct sense circuit wiring with no shorts-to-power or terminal issues.

Can I Still Drive With P0690?

P0690 involves the ECM/PCM power relay sense circuit reporting a high electrical condition, which can affect how reliably the control module powers up or stays powered. Driving may be possible if the vehicle runs normally, but treat it as potentially reliability-critical: intermittent stalling, a no-start, sudden reduced power, or multiple warning lamps can occur depending on vehicle design. If the engine stalls, cranks without starting, or you notice loss of power assistance or other safety-related warnings, do not continue driving; stop safely and have the circuit diagnosed.

What Happens If You Ignore P0690?

Ignoring P0690 can lead to worsening electrical connection damage, recurring no-start events, or unexpected stalls if the power relay sense issue is intermittent. The ECM/PCM may mismanage power-up/power-down logic, potentially triggering additional fault codes, driveability complaints, and repeated battery drain concerns (varies by vehicle). Continued operation with unstable power/ground integrity can also complicate future diagnosis by creating multiple secondary symptoms that mask the original circuit-high condition.

Related Relay Ecm/pcm Codes

Compare nearby relay ecm/pcm trouble codes with similar definitions, fault patterns, and diagnostic paths.

• P0687 – ECM/PCM Power Relay Control Circuit High
• P0891 – TCM Power Relay Sense Circuit High
• P0689 – ECM/PCM Power Relay Sense Circuit Low
• P0887 – TCM Power Relay Control Circuit High
• P0688 – ECM/PCM Power Relay Sense Circuit/Open
• P0617 – Starter Relay Circuit High

Key Takeaways

• P0690 indicates an electrical circuit high condition in the ECM/PCM power relay sense circuit, not a confirmed relay or module failure by itself.
• Most successful fixes start with wiring, connectors, terminals, and power/ground integrity checks before replacing parts.
• Short-to-power conditions, poor terminal fit, and corrosion can all drive a false high sense reading and may be intermittent.
• Because the circuit relates to module power management, symptoms can range from none to stall/no-start depending on vehicle strategy.
• Confirm the root cause with test-driven diagnostics and service information specific to the vehicle before authorizing major repairs.

Vehicles Commonly Affected by P0690

• Vehicles using an ECM/PCM-controlled main power relay with a dedicated sense/feedback circuit
• Platforms with under-hood fuse/relay centers exposed to moisture, heat cycling, or vibration
• Vehicles with prior electrical repairs involving splices, aftermarket accessories, or disturbed harness routing (varies by vehicle)
• High-mileage vehicles where terminal tension, relay sockets, or ground points may degrade over time
• Vehicles operated in corrosive environments where connector fretting or oxidation is more likely
• Applications with tight packaging that increases harness chafe risk near brackets, battery trays, or fuse boxes
• Vehicles with known intermittent power complaints (stall/no-start) where power-feed integrity must be verified
• Systems that monitor relay state using a sense wire separate from the relay control circuit

FAQ

Does P0690 mean the ECM/PCM power relay is bad?

No. P0690 only indicates the ECM/PCM power relay sense circuit is reading a high electrical condition. A failed relay is one possibility, but wiring shorts-to-power, connector/terminal issues, or power/ground faults can produce the same result. Testing should confirm the cause before replacing the relay.

What does “circuit high” mean for this code?

“Circuit high” means the monitored sense signal is higher than expected for the operating state the ECM/PCM is commanding or expecting. Common electrical reasons include a short-to-power, an open or weak ground reference, incorrect backfeed from another circuit, or connector/terminal problems that create an unintended high reading.

Can a weak battery cause P0690?

A weak battery more commonly contributes to low-voltage conditions, but poor battery connections, unstable system voltage, or power distribution faults can indirectly contribute to abnormal relay sense behavior depending on vehicle design. The best approach is to verify battery and charging system health and then focus on the relay sense circuit for shorts-to-power and connection integrity.

Why does P0690 sometimes come and go?

Intermittent P0690 events are often caused by vibration-sensitive faults such as loose relay fitment, poor terminal tension, fretting corrosion, harness chafing that intermittently contacts power, or a marginal ground connection. Confirm by inspecting connectors closely and performing a wiggle test while logging the related relay sense parameter (if available) and system voltage behavior.

Should I replace the ECM/PCM if the code keeps returning?

Only after verifying, with documented testing, that all ECM/PCM powers and grounds are correct under load, the relay operates correctly, and the sense circuit has no short-to-power, backfeed, or terminal issues. Module replacement is a last step because wiring/connection faults are common, and replacing a module without correcting the underlying circuit-high condition can result in the same code returning.

If P0690 is present, focus on proving why the ECM/PCM power relay sense circuit is reading high using service information, careful connector inspection, and load-based electrical testing before replacing major components.