Damaged, chafed or corroded wiring or connector on the torque control cut signal line between the engine ECU and transmission control unit; Open circuit or short to voltage in the signal wire, including a loose terminal or water ingress in a connector; Poor power or earth supply to the engine ECU or transmission control unit affecting the signal level; Fault inside the transmission control unit holding the signal line high; Fault inside the engine ECU output or input stage; Outdated control unit software where a known update addresses the fault, depending on model and year.

P1115

Engine Torque Control Cut Signal Circuit High Input.

Subaru
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
1: AreaFuel and air metering
15: FaultThe specific fault in that area

What it means

On Subaru, P1115 means the engine control unit has seen a high input on the engine torque control cut signal circuit. This is the signal line between the engine ECU and the automatic transmission control unit, used to reduce engine torque briefly during gear changes. The ECU set the code because the voltage on that line was higher than expected, or the signal was not what it expected.

Symptoms

Malfunction indicator lamp on
Harsh or flared gear changes on automatic models
Reduced or inconsistent engine response during upshifts or downshifts
Transmission warning lamp or limp-home behaviour on some models
Other transmission or engine communication codes stored alongside

Possible causes

Damaged, chafed or corroded wiring or connector on the torque control cut signal line between the engine ECU and transmission control unitlikely
Open circuit or short to voltage in the signal wire, including a loose terminal or water ingress in a connectorlikely
Poor power or earth supply to the engine ECU or transmission control unit affecting the signal levelpossible
Fault inside the transmission control unit holding the signal line highpossible
Fault inside the engine ECU output or input stagerare
Outdated control unit software where a known update addresses the fault, depending on model and yearrare

How to diagnose

Read all stored codes and freeze frame data, noting whether transmission codes are also present, then record and clear to see if P1115 returns.
Check for technical service information relevant to the model, engine and year, as the exact circuit layout varies.
Visually inspect the wiring harness and connectors between the engine ECU and transmission control unit for chafing, heat damage, corrosion, water and bent or pushed-back pins.
With the connectors disconnected, check the signal wire for continuity, and for shorts to voltage and earth, using the wiring diagram for the specific model.
Check the supply and earth circuits of both control units for voltage drop and good connection.
Check battery condition and charging voltage, as low voltage can cause spurious signal faults.
Wiggle-test the harness with live data or a monitor connected to see if the fault appears intermittently.
If wiring and supplies are sound, check whether a software update is available before suspecting a control unit.

How to fix

Repair or replace damaged wiring in the torque control cut signal circuit, using proper soldered and sealed joins.
Clean, re-seat or replace corroded or loose connectors and terminals.
Restore faulty power or earth connections to the control units.
Replace the transmission control unit or engine ECU only after the wiring and supplies are confirmed good, and have it coded as required.
Apply a manufacturer software update if one is confirmed to address this fault.

Can I keep driving?

Medium severity

The car can usually be driven carefully to a workshop, but expect rough shifting and reduced response. Have it checked soon, as harsh gear changes can cause extra transmission wear.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.