What does P1781 mean on a Chevy?

P1781. Engine Torque Signal Circuit. Applies to Impala, Malibu, Monte Carlo, Lumina.

What causes P1781 on a Chevy?

Open or short in the engine torque signal circuit between PCM and transmission Corroded PCM or transmission pass-through connectors Faulty powertrain control module torque output Chafed torque signal wiring near the transmission Faulty transmission control module input

How do I fix P1781 on a Chevy?

Monitor the engine torque signal parameter with a Tech2 scan tool Inspect PCM and transmission connectors for corrosion or damage Test the torque signal circuit for opens, shorts to ground, and shorts to voltage Repair wiring and confirm valid torque signal on the scan tool Replace the faulty module only after circuit testing proves it out

Code

P1781

Engine Torque Signal Circuit

Category: Powertrain - Transmission
Severity: Check Engine Light
Applies to: Impala, Malibu, Monte Carlo, Lumina
Related: No single generic twin. See OBD Codes List

What it means

P1781. Engine Torque Signal Circuit. This Chevy-enhanced code applies to Impala, Malibu, Monte Carlo, Lumina.

Findings, check these first

Open or short in the engine torque signal circuit between PCM and transmission
Corroded PCM or transmission pass-through connectors
Faulty powertrain control module torque output
Chafed torque signal wiring near the transmission
Faulty transmission control module input

Standard procedure

Monitor the engine torque signal parameter with a Tech2 scan tool
Inspect PCM and transmission connectors for corrosion or damage
Test the torque signal circuit for opens, shorts to ground, and shorts to voltage
Repair wiring and confirm valid torque signal on the scan tool
Replace the faulty module only after circuit testing proves it out

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Sources and review

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Last updated 2026-09-13.

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