By iCarsoft Official Store Technical Team, Automotive Diagnostics Editors · Updated September 4, 2026 · OEM technical references checked
Quick Answer
The P0689 code means ecm/pcm power relay sense circuit low. It does not prove the power relay is defective, the PCM has failed, or the low event occurred at the battery rather than the monitored sense path. Save the scan, identify the exact architecture, and test the physical and electrical paths before selecting a repair.
What Does the P0689 Code Mean?
P0689 is standardized as ECM/PCM Power Relay Sense Circuit Low. It names a monitored result, not a guaranteed failed part. The reporting module, suffix and companion faults determine the relevant test branch.
A controller can command a main power relay, monitor its switched output through a separate sense path and supervise voltage during start and shutdown. Command, contacts, fused output, ground and sense input remain distinct test points.
Read each suffix as its exact monitor classification, not a universal physical direction. Confirm the designation, units, signal source and test state before comparing scan data with an external measurement.
A Ford investigation attachment lists P0689 as ECM/PCM Power Relay Sense Circuit Low. GM preliminary information PIT5643 describes intermittent reduced power, stall or no-start with P0689/P1682 caused by a loose underhood fuse-block terminal on the named vehicles. That connector and location must not be transferred to another application.
Separate P0689 from adjacent fault families
| Code | General description | Key distinction |
|---|---|---|
| P0689 | ECM/PCM power relay sense circuit low | Low result on the relay-output sense path. |
| P0688 | ECM/PCM power relay sense circuit open | Open or missing sense-path classification. |
| P0690 | ECM/PCM power relay sense circuit high | High result on the same general sense family. |
| P0686 | ECM/PCM power relay control circuit low | Low branch for relay command/control, not P0689. |
Record the complete P0689 description. The suffix, reporting module and companion faults can change the diagnostic path. Current manufacturer evidence governs when the queue wording conflicts.
P0689 Symptoms and Likely Causes
P0689 symptoms depend on fault status and the fallback strategy. Record what the driver and modules reported. A symptom list is not a parts list.
Record whether the starter operates and which modules remain online.
Save the first fault and module reset history before cycling the key.
A shared feed, terminal or ground may affect several controllers together.
Relay sense can be monitored after key-off, so preserve timing and wake-up behavior.
Practical cause-checking order
- Accessible connection: Loose, spread, corroded or heat-damaged relay, fuse-block, PCM or battery terminal.
- Circuit or shared path: Low loaded voltage, high resistance or an open in the fused relay-output, sense, feed or ground path.
- Supporting system: Battery condition, main-feed issue or accessory load causing a module supply event.
- Named component: Power relay that fails contact-voltage-drop or commanded-operation testing.
- Controller or software: PCM input, power-management logic or calibration issue after every external path passes.
Did P0689 appear after recent battery, fuse-block, relay, starter, controller, accessory, ground or harness work? Recheck disturbed connectors, grounds, hoses, fluids, part numbers and setup steps for the ECM/PCM power-relay sense, switched output and module supply. Record battery and software history; a post-repair code does not prove the new part is defective.
How Serious Is P0689, and Can You Drive?
Arrange diagnosis promptly. When the warning is steady, operation remains normal and the owner's manual permits it, a short light-load trip to a repair facility may be reasonable. Avoid demanding use until the ECM/PCM power-relay sense, switched output and module supply is understood. P0689 does not provide a universally safe distance.
Record temperature, load, speed, start state and recent service. Do not reproduce a severe symptom on public roads; another warning can make the situation more urgent.
Stop and arrange a tow if the engine stalls, starting becomes unreliable, steering or braking assistance changes, a main power connection overheats, smoke appears, or module resets make operation unsafe.
A power-relay circuit can carry substantial current and may remain live after key-off. Follow module sleep and battery-disconnect procedures, use fused probes and never bypass a relay or fuse for a road test.
How to Diagnose P0689 in the Right Order
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Save the complete fault record
Scan before clearing. Save P0689 wording, suffix, reporting module, status, freeze frame, companion codes, supply voltage and available data for the ECM/PCM power-relay sense, switched output and module supply. Record failure order, recent repairs and restart behavior for later comparison.
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Identify the VIN-specific monitor and architecture
Use the VIN, engine, transmission and equipment codes to obtain the current wiring diagram, connector views, monitor description and bulletins. A controller can command a main power relay, monitor its switched output through a separate sense path and supervise voltage during start and shutdown. Command, contacts, fused output, ground and sense input remain distinct test points. Confirm software identifiers and service-action eligibility directly; a bulletin for one application does not establish coverage for another.
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Inspect the accessible physical path
Follow the safety procedure, then inspect connectors, locks, seals, terminals, clips and harness routing for the ECM/PCM power-relay sense, switched output and module supply. Look for heat, abrasion, fluid entry, corrosion, tension and unsuitable prior repairs. Check the supporting mechanical, air, exhaust, fluid or vacuum path named in the service information. Photograph evidence before correcting it.
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Prove circuits and physical conditions
Use the digital multimeter, fused load tool, low-current clamp or scope when specified and terminal-tension gauges for the exact connector as the exact procedure requires. Prove feeds, grounds and references under the specified load, then test signal or control integrity at the correct states. Isolate components before resistance tests. Never bridge a controller pin to battery or ground, and do not substitute a continuity beep for a load, pressure or waveform test.
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Compare supported command and response
Compare ignition state, PCM voltage, relay command, wake/sleep status and faults across modules while monitoring the switched relay output at the specified test point. Capture startup and key-off transitions rather than checking only steady idle. Compare scan evidence with the external measurement and companion faults. A command does not prove physical movement, pressure, current, temperature or torque. A missing PID or active test is a coverage limitation, not evidence that the vehicle component failed. Stop any test if operation becomes unsafe.
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Choose the supported repair and setup
Repair the failed path and correct the reason for damage. Confirm part application, required setup authorization and any relearn. Consider a controller only after its powers, grounds, inputs, outputs and service information pass.
Specifications are vehicle-specific. There is no universal voltage, resistance, current, pressure, waveform, timing, temperature, percentage, learned value or drive cycle for P0689. Test state, connector location and system design change what a valid value means. Use only specifications for the exact VIN and do not transfer the OEM example in this article to another application.
P0689 Repairs and Typical Costs
The correct P0689 repair follows the failed test. Wiring, a physical repair, a proven component, software and controller work are different outcomes. Do not replace an assembly from the generic code alone.
After installation, recheck connector seating, harness clearance, fluid or mechanical setup and every required learn. If an OEM bulletin appears relevant, document vehicle eligibility, installed calibration and prescribed action. The existence of the bulletin in the references does not promise warranty, free repair or a software cure for other vehicles.
| Possible path | Current US estimate |
|---|---|
| Restore a loose terminal, fuse-block connection, ground or relay-output path | VIN-specific quote |
| Correct a proven battery or main-feed voltage-drop problem | VIN-specific quote |
| Replace the power relay only after contact and command tests fail | VIN-specific quote |
| Address PCM input or software only after powers, grounds and external sense wiring pass | VIN-specific quote |
There is no single national P0689 repair price because these rows are alternative outcomes. Ask for an itemized estimate showing diagnostic time, parts, labor, fluids, service-information access and verification. Location, taxes, related damage and warranty eligibility change the total. Do not add the rows together or authorize an assembly without the supporting failed test.
Using iCarsoft CR Max P for P0689
On a supported vehicle, iCarsoft CR Max P can retrieve accessible module faults, save available freeze frame, display ECU-provided live data and create a diagnostic report. For P0689, preserve the original evidence and compare related modules before clearing an erasable record.
Preserve the ECM/PCM power-relay sense, switched output and module supply evidence
iCarsoft CR Max P
Review supported codes and relevant live data together. Confirm the exact VIN, controller access, PIDs and any requested active test with iCarsoft before purchase; generic product capabilities do not guarantee a P0689-specific function.
Check current CR Max P price and availabilityCheck CR Max P compatibility by VINThe official product page describes full-system diagnosis, available freeze frame/live data, reports, topology and supported bidirectional functions; every function remains vehicle, ECU and software dependent. Supported topology and coding availability varies by vehicle and ECU and requires VIN confirmation. Follow OEM prerequisites and stop for abnormal operation.
Know the measurement boundary. The scanner reports information supplied by the vehicle. It does not directly prove terminal tension, circuit load capacity, leakage, pressure, temperature, mechanical travel or internal condition in the ECM/PCM power-relay sense, switched output and module supply. It also cannot replace the digital multimeter, fused load tool, low-current clamp or scope when specified and terminal-tension gauges for the exact connector when the OEM procedure requires them. Interpret commanded and reported values alongside measured evidence.
Verify the P0689 Repair
After repair, verify connectors, harness clearance, setup and controller supply. Save post-repair findings, then clear only erasable records through the approved procedure. Battery disconnection is not a repair.
Run the manufacturer's applicable verification conditions in a safe workshop or route. Compare the original operating state with current data for the ECM/PCM power-relay sense, switched output and module supply, and check current and pending faults in related modules. One clean start or idle period does not prove that every conditional monitor has completed.
If P0689 returns, compare its suffix, status, failure order and operating conditions with the saved baseline before replacing another part. Revisit the failed branch and inspect anything disturbed. Keep mechanical repair, monitor completion, readiness and local inspection eligibility as separate outcomes.
A permanent P0689 can remain immediately after a successful repair. If the vehicle stores it as a permanent DTC, a scan tool or battery disconnect cannot erase it. Once current and pending faults are absent, the OBD system removes the permanent record only after the applicable monitor reruns and passes.
Related ECM/PCM Power-Relay Sense, Switched Output And Module Supply Code Guides
P0689 Frequently Asked Questions
Does P0689 mean the named component is bad?
No. P0689 describes ecm/pcm power relay sense circuit low, not a confirmed part. It also does not prove the power relay is defective, the PCM has failed, or the low event occurred at the battery rather than the monitored sense path. Test accessible wiring, supplies, grounds and supporting physical conditions, then follow the exact monitor tree. Replace a component only when its branch fails or an applicable OEM action specifically supports it.
What should I check first for P0689?
Save every module's codes and freeze frame before clearing. Confirm the full definition, suffix and VIN architecture. Then inspect recent battery, fuse-block, relay, starter, controller, accessory, ground or harness work, connectors and shared supplies. Those facts determine whether the next test needs the digital multimeter, fused load tool, low-current clamp or scope when specified and terminal-tension gauges for the exact connector or a manufacturer-specific functional procedure.
Can I drive with the P0689 code?
Only consider a short light-load trip when operation is normal and the owner's manual permits it. Stop if the engine stalls, starting becomes unreliable, steering or braking assistance changes, a main power connection overheats, smoke appears, or module resets make operation unsafe. The code number cannot establish a safe mileage allowance, and another warning can make the situation more urgent.
Why did P0689 return after a part was replaced?
The original circuit or supporting-system fault may remain, the part or setup may be wrong, or the first diagnosis may have confused a monitored result with a failed component. Compare the new failure conditions with the saved record and recheck every disturbed connection before buying another part.
How much does a P0689 repair cost?
A VIN-specific estimate is required because diagnosis may lead to wiring, a supporting physical repair, a verified component, software or a controller. Ask which failed test supports the quote and whether diagnosis, taxes, setup and post-repair verification are included.
Can CR Max P diagnose and clear P0689?
On a supported vehicle, CR Max P can organize available faults, freeze frame, live data and reports, and can clear erasable records after repair. Confirm exact ECU coverage. It cannot force-clear a permanent DTC or replace physical measurements for the ECM/PCM power-relay sense, switched output and module supply.
The iCarsoft Official Store Technical Team maintains the store's fault-code library. This guide organizes published manufacturer evidence and verified product information; it does not document a hands-on test of a particular vehicle or claim an individual engineer's review.
Technical and cost references
- Ford PE13-003 technical attachment. Lists the standardized P0689 description as ECM/PCM Power Relay Sense Circuit Low.
- GM Preliminary Information PIT5643, 2018. Documents an application-specific loose fuse-block terminal associated with P0689/P1682 and intermittent reduced-power, stall or no-start symptoms.
- California Bureau of Automotive Repair — On-Board Diagnostic Test Reference. Permanent DTCs are removed by the vehicle after applicable verification, not by a scan-tool erase command.
Product information: Official iCarsoft CR Max P page.
Editorial note: General diagnostic education, not a substitute for the owner's manual, current VIN-specific service information or professional inspection. Test limits, procedures, coverage and costs vary. Related articles provide context; apply only the specifications and repair procedures that match the vehicle. No universal failure rate, repair price or outcome is implied.
