P1894

What it means

P1894 is a GM-specific code meaning the engine torque signal is reading high voltage. On Chevrolet models that use it, the transmission control unit receives an engine torque signal from the engine control module to help manage shift feel and torque reduction. The code sets when the transmission control unit sees that signal circuit stuck high or out of its expected range. The exact circuit layout and which module reports it depend on the model, engine and transmission.

Symptoms

• Harsh, delayed or flared gear shifts
• Transmission stuck in a fixed gear or limp mode
• Gearbox warning light or check engine light on
• Poor or inconsistent shift quality under load
• Other engine or transmission communication codes stored alongside

Possible causes

• Wiring fault on the engine torque signal circuit, such as a short to voltage or chafed insulationlikely
• Corroded, loose or damaged connector terminals at the engine control module or transmission control unitlikely
• Poor power or earth supply to the engine control module or transmission control unit, causing a distorted signalpossible
• Faulty engine control module output driver for the torque signalpossible
• Faulty transmission control unit input circuitpossible
• Outdated software in the engine or transmission control unit where a manufacturer bulletin appliesrare

How to diagnose

1. Read all stored and pending codes and note the freeze frame data, including whether other engine or transmission codes are present.
2. Check for manufacturer bulletins and wiring diagrams for the specific model, engine and transmission, to confirm which circuit carries the torque signal.
3. Visually inspect the harness and connectors between the engine control module and transmission control unit for chafing, heat damage, water ingress and bent or pushed-back pins.
4. Check battery condition and charging voltage, then test the power and earth supplies to both control units.
5. With the ignition on, measure the torque signal circuit voltage at the transmission control unit and compare it with the specified value.
6. Check the signal circuit for a short to voltage with the connectors disconnected, and check its continuity end to end.
7. Use a scan tool to view live torque signal data while changing engine load, and use an oscilloscope to check the signal pattern if available.
8. Clear the code, road test and recheck to see if it returns, before considering control unit faults.

How to fix

• Repair or replace damaged wiring on the torque signal circuit.
• Clean or replace corroded or damaged connectors and terminals.
• Restore good power and earth connections to the control units.
• Replace the faulty engine control module or transmission control unit only after wiring and supplies are proven good, and program it as required.
• Update the control unit software if an outdated calibration is a known cause for that model.

Can I keep driving?

This code for other makes

• P1894BuickEngine Torque Signal High Voltage
• P1894CadillacEngine Torque Signal High Voltage
• P1894GMEngine Torque Signal High Voltage
• P1894GMCEngine Torque Signal High Voltage
• P1894OldsmobileEngine Torque Signal High Voltage
• P1894SaturnEngine Torque Signal High Voltage

Nearby codes

• P1893ChevroletEngine Torque Signal Low Voltage
• P1895ChevroletTCM To ECM Torque Reduction Circuit