Code
C1291
MITSUBISHI
C — Chassis
Reverse switch
Views:
UK: 12
EN: 16
RU: 32
AI status
Completed
Completed
100%
Causes
- Failed or intermittent reverse (backup) switch
- Damaged wiring or connector (open, short to ground, short to battery)
- Corroded or loose connector terminals
- Blown fuse or related power supply issue
- Faulty body or transmission control module (rare)
- Mechanical linkage problem preventing switch actuation
Symptoms
- Stored C1291 trouble code (may illuminate ABS/traction or warning lamp depending on system)
- Backup lights do not illuminate or remain on constantly
- Reverse-related features (parking sensors, camera, auto-safety interlocks) do not engage
- Intermittent operation of reverse-related systems
What to check
- Perform a safety check: park on level ground, chock wheels, apply parking brake and follow manufacturer safety procedures before tests.
- Scan tool: read and record freeze frame and live data for reverse switch input while selecting reverse gear.
- Visually inspect switch and connector for corrosion, bent pins, water intrusion, and secure mounting.
- Check backup lights operation by selecting reverse with ignition on; have an assistant observe lights.
- Check fuses and related power/ground circuits for the reverse/backup circuit.
- Measure continuity and resistance of switch wiring from switch connector to the control module connector.
Signal parameters
- Typical switch signal: open/ground or open/12V depending on model (verify factory wiring diagram)
- Expected voltage at switch connector with ignition ON and gear in Reverse: ~12 V or ~0 V (model-dependent; confirm with wiring diagram)
- Expected resistance: near 0 Ω when switch closed (actuated) and very high/OL when open
- No parasitic voltage present on signal circuit when switch is open
Diagnostic algorithm
- Confirm DTC: Connect a scan tool, read C1291, clear the code and attempt to reproduce by selecting reverse gear while observing live data.
- Visual inspection: Inspect reverse switch, wiring harness, and connectors for damage, corrosion, or water entry. Repair any obvious damage.
- Verify backup lights: With ignition ON, have an assistant place the transmission in Reverse. If backup lights don’t operate, suspect switch or power feed.
- Check power/ground: Verify the feed fuse and any fused power/ground to the switch are present and correct per wiring diagram.
- Backprobe switch: Measure the signal circuit at the switch while operating gear selector. Compare voltage/resistance to expected values from the service manual.
- Isolate circuit: If signal is incorrect at the switch, replace the switch. If correct at the switch but incorrect at the ECU connector, inspect/repair wiring between switch and ECU (check continuity and shorts).
- Repair connector/wiring: Repair or replace damaged connectors or wiring. Use proper crimping, soldering, and sealing methods to maintain reliability.
- ECU check: If wiring and switch are good and the fault persists, consult wiring diagrams and consider module input testing or module replacement only after confirming other components.
- Verify repair: Clear codes and test drive/operate to ensure C1291 does not return and reverse-related functions work correctly.
Likely causes
- Corroded/loose connector at the reverse switch
- Open or shorted wiring in the reverse switch circuit
- Faulty reverse switch
Fault status
Status
Reverse switch circuit malfunction detected
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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