Code
C1541
MITSUBISHI
C — Chassis
Fail safe relay stuck ON
Views:
UK: 12
EN: 12
RU: 11
AI status
Completed
Completed
100%
Causes
- Stuck, welded or mechanically jammed fail-safe relay
- Relay contacts fused closed due to arcing or overheating
- Short to battery (power feed stuck ON) in relay output circuit
- ECU/ABS module driver transistor or relay driver stuck ON
- Damaged wiring or short between relay control and constant power
- Corroded or poor relay socket/connector causing unintended continuity
Symptoms
- ABS/VDC/VSA or general warning lamp illuminated
- Vehicle in reduced function or fail-safe mode for affected system
- Pump or actuators operating when they should be off (audible noise)
- Battery drain when ignition is off (relay stuck closed)
- Intermittent or persistent fault code C1541 stored
What to check
- Read stored DTCs and freeze frame data with a diagnostic scanner
- Visual inspection of fail-safe relay, socket and related wiring for heat damage or corrosion
- Listen for relay click when cycling ignition and when commanded by scanner
- Check fuses and power supply to the relay location
- Measure supply voltage at relay power terminal (should be battery voltage with ignition on)
- Check continuity between relay output terminal and the controlled circuit with relay removed
Signal parameters
- Battery supply at relay common terminal: ~12 V (with ignition ON)
- Control signal from ECU to relay coil: toggles between near 0 V and battery voltage (per vehicle wiring)
- Coil resistance: compare to service manual specification (typical relays vary)
- Continuity between relay output and component should be open with relay removed (unless stuck)
- Measured current draw on supply circuit when relay energized versus de-energized (compare to spec)
Diagnostic algorithm
- Connect a diagnostic scanner, record C1541 and any related codes, and note freeze-frame data.
- Perform a visual inspection of the relay, socket, wiring harness and connectors for damage, corrosion or signs of overheating.
- With ignition OFF, remove the fail-safe relay and inspect contacts. Check for welding, carbon buildup or mechanical seizure.
- Using an ohmmeter, measure the relay coil resistance and compare to the service manual; bench-test the relay by applying proper voltage and verify switching action.
- With the relay removed, check continuity between the relay output terminal and the powered circuit — there should be no battery continuity when relay is absent/unenergized.
- With a DVOM or oscilloscope, monitor the ECU control line to the relay while commanding the system via scanner: verify the module is not outputting a constant drive signal when it should be off.
- Check for short to battery on the relay output wiring (backprobe harness for constant 12 V when relay should be off). Repair shorted wiring or connectors as needed.
- Substitute a known-good relay of the correct specification; clear codes and re-test system operation and stored faults.
- If the relay and wiring check good but the fault returns, suspect ECU/ABS module driver fault. Perform module-level diagnostics per service manual and consider module repair/replacement.
- After repair, clear codes, complete a road test and verify no recurrence of C1541.
Likely causes
- Failed fail-safe relay (contacts welded or coil short)
- Shorted power feed in harness to relay output terminal
- ECU internal driver fault forcing relay ON
- Corroded connector or poor ground keeping relay energized
- Incorrect replacement relay or wrong relay fitted
Fault status
Status
Fail-safe relay circuit indicates relay is ON when it should be OFF. Possible stuck relay, short to power, or module driver fault. Inspect relay, wiring and control module.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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