Code
P1115
SUBARU
P — Powertrain
Engine Torque Control Cut Signal Circuit High Input
AI status
Completed
Completed
100%
Causes
- Short to battery/12V on the torque-control-cut signal wire
- Open circuit or damaged wiring (intermittent high due to poor contact)
- Corroded or loose connector at the switch or ECM
- Faulty torque-cut related switch or sensor (e.g., brake or clutch switch depending on system design)
- Aftermarket wiring or incorrect repairs tapping into the circuit
- Internal ECM input circuit fault
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Reduced engine torque or unexpected torque management behavior
- Cruise control disabled or inoperative
- Unexpected or harsh engine cut/hesitation during events where torque control should be applied
- Possible no-start or limp behavior in extreme cases (depending on vehicle logic)
What to check
- Read and record freeze frame and freeze data with a scan tool; note conditions when code set
- Inspect wiring harness and connectors for damage, corrosion, pin push-out, or aftermarket taps
- Backprobe the torque-cut signal wire at the ECM and at the related switch while operating the switch (brake/clutch) to observe behavior
- Measure DC voltage of the signal circuit vs. ground with ignition ON and while actuating the related switch
- Check for continuity/short to battery: resistance from signal wire to battery positive with ignition off (power off) and harness disconnected
- Disconnect the related switch or sensor: see if the code clears or behavior changes to help isolate component vs. wiring
Signal parameters
- Typical inactive signal voltage: approx. 0–1 V (depends on system; many torque-cut inputs are pulled to ground when active)
- Fault condition: signal voltage significantly higher than expected (often >5 V or close to battery voltage) reported as 'High Input'
- Expected behavior: voltage changes state when related switch (brake/clutch) is actuated; look for clean transitions without noise
- Reference: verify with manufacturer service information for exact thresholds and pull-up/pull-down design
Diagnostic algorithm
- Verify the code: Use a scan tool to confirm P1115 and record freeze frame. Clear codes and attempt to reproduce.
- Visual inspection: Inspect connectors and wiring along the torque-cut signal circuit for damage, corrosion, or recent repairs. Pay attention to harness routing where it could chafe or contact constant-12V sources.
- Identify circuit function: Confirm which switch/sensor provides the Engine Torque Control Cut signal (brake switch, clutch switch, or dedicated torque-cut switch) using the vehicle service manual.
- Signal monitoring: Backprobe the signal at the ECM and at the switch. With ignition ON, observe voltage and operation while actuating the switch. Note whether the signal reads high (near battery) and whether it changes state as expected.
- Isolation: Disconnect the related switch/sensor and check whether the code clears or the signal changes. If disconnecting the switch removes the high input, suspect the wiring harness between the switch and ECM or the switch itself.
- Short-to-power check: With harness disconnected, measure resistance between the signal wire and battery positive. A low resistance indicates a short to power that must be traced and repaired.
- Repair wiring or connector faults: Repair/chassis-ground any chafed wiring, replace damaged connectors, and replace faulty switch if bench/functional testing confirms failure.
- Verify repair: After repairs, clear codes, perform a road/functional test to reproduce original conditions, and confirm the code does not return.
- ECM evaluation: If wiring and component checks are good and the fault persists, consult manufacturer procedures for ECM input testing and replacement; confirm ECM fault with appropriate bench diagnostics before replacement.
Likely causes
- Signal wire shorted to 12V (most common)
- Corroded/loose connector at the switch or ECM
- Failed brake or clutch switch that supplies the signal
- Wiring chafed and contacting vehicle power
- ECM internal fault (least likely; confirm after wiring and component checks)
Fault status
Status
The ECM detected a higher-than-expected voltage on the Engine Torque Control Cut input circuit (signal read as 'High Input'). This indicates a wiring short to battery, faulty switch, poor connector contact, or less commonly an internal ECM input fault. The condition can disable expected torque-cut/torque-management functions and will trigger the MIL until the underlying circuit issue is corrected.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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