01 U0001 High Speed CAN Communication Bus • 02 This Is Why It’s Almost Impossible To Sink A Modern Cruise … • 03 The Latest Advances in Shipbuilding: How Technology is Shap… • 04 Exhaust Speakers: The Secret to Making Your Car Sound More … • 05 This Is Why Your Car’s EGR Valve Is Stuck • 06 Troubleshooting Black Smoke: Diagnosing Fuel-to-Air Issues … • 07 Engine Cranking Noises: Guide to Identifying and Tackling C… • 08 What You Need to Know: Driving with the ABS Light On and Ho… • 09 Spark Plug Dilemma: Replace All or Just the Bad Ones? Let's… • 10 What Happens If You Drop The Anchor At Full Speed? •

DTC codes / Subaru codes / P1104

P1104 · SubaruEngine Torque Control Signal Circuit Malfunction

P1104 on Subaru vehicles indicates that the engine control module (ECM) has detected a malfunction in the circuit that carries the engine torque control signal, which is used to coordinate torque delivery between the engine and transmission. The ECM monitors the signal line for expected voltage or communication patterns and sets this code when the signal is missing, erratic, or out of range.

SystemPowertrain
Code typeSubaru specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • Rough or inconsistent engine performance, especially during acceleration or gear changes.
  • Hesitation or delayed response when pressing the accelerator.
  • Transmission may shift harshly or fail to engage smoothly due to incorrect torque signals.
  • In some cases, the vehicle may enter limp mode, limiting engine power.

Common causes, most likely first

  1. Faulty or dirty electrical connector at the engine torque control signal circuit, often due to corrosion or loose pins.
  2. Damaged wiring harness, such as chafed or broken wires between the ECM and transmission control module (TCM) or other components.
  3. Failed engine torque control sensor or associated solenoid, if equipped, sending incorrect signals.
  4. Malfunctioning ECM or TCM, though this is less common and should be diagnosed last.
  5. Poor ground connection for the circuit, causing voltage irregularities.
  6. Aftermarket modifications or improper repairs that interfere with the signal wiring.

How to diagnose and fix it

  1. Inspect and clean the electrical connectors related to the engine torque control circuit, checking for corrosion or loose pins.
  2. Perform a visual inspection of the wiring harness for damage, rubbing, or breaks, and repair as needed.
  3. Use a multimeter to check for continuity and voltage on the signal wire according to the factory service manual specifications.
  4. Test the engine torque control sensor or solenoid (if applicable) for proper resistance and operation.
  5. Check and clean ground connections associated with the ECM and TCM.
  6. If all external circuits test good, substitute a known-good ECM or TCM to rule out internal failure.
  7. After repairs, clear the code and perform a road test to verify the fix and ensure the code does not return.

Common Misdiagnosis Traps for P1104

  • A loose or corroded connector at the transmission or ECM is frequently the root cause, yet many technicians replace expensive sensors without first checking connector integrity.
  • The engine torque control signal is often confused with the throttle position signal, leading to unnecessary throttle body replacements when the actual fault lies in the torque signal circuit.
  • On some Subaru models, this code can be triggered by a failing transmission control module (TCM) even when the engine runs perfectly, so testing the TCM is essential before condemning the ECM.
  • Aftermarket electrical accessories or poor previous repairs can introduce interference on the signal line, causing intermittent P1104 without any hard failure.
  • A weak battery or charging system issue can cause voltage drops that mimic a signal circuit fault, so always verify battery and charging system health first.

Can I keep driving with P1104?

You can usually drive the vehicle with P1104, but avoid aggressive acceleration or heavy loads because the malfunction may cause unpredictable torque delivery and affect transmission shifting. If the vehicle enters limp mode or performance degrades noticeably, seek service promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Subaru vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage