P1894

What it means

P1894 means the transmission control side of the system saw the engine torque signal from the engine control module sitting at a higher voltage than expected. This signal tells the transmission how much torque the engine is making so it can set line pressure and shift feel. The exact circuit layout, and whether the transmission control is a separate module or built into the engine control module, depends on the model and year.

Symptoms

• Harsh or firm gear changes, especially under light throttle
• Transmission stuck in a fixed gear or a default shift pattern
• Check engine light or transmission warning light on
• Flares or slipping on shifts
• Poor fuel economy if the torque converter clutch is inhibited
• Other transmission or engine communication codes stored alongside it

Possible causes

• Torque signal wire shorted to voltage or chafed against another live circuitlikely
• Poor connection, corroded or spread terminals at the engine or transmission control module connectorslikely
• Damaged wiring harness between the engine and transmission control modules, possibly where it passes the bellhousing or bulkheadpossible
• Fault in the engine control module output driver that sends the torque signalpossible
• Fault in the transmission control module input circuitpossible
• Low or unstable system voltage from a weak battery or poor earths upsetting the signalrare

How to diagnose

1. Read all stored codes and freeze frame data, and note any engine or communication codes that accompany P1894
2. Check battery condition and charging voltage, and inspect the main earth connections
3. Visually inspect the harness and connectors at the engine and transmission control modules for chafing, corrosion, moisture or pushed-back pins
4. With the ignition on, back-probe the torque signal circuit and compare against the manufacturer's wiring diagram for your model; look for a stuck-high or fixed voltage
5. Check the signal circuit for a short to voltage with both modules unplugged, and test continuity end to end
6. Use a scan tool or oscilloscope to confirm the signal changes with engine load rather than staying fixed high
7. If wiring is sound, test the signal at the engine control module output to separate a driver fault from a transmission-side fault
8. Clear the code, road test and recheck whether it returns

How to fix

• Repair or replace damaged wiring on the torque signal circuit, sealing and securing the harness afterwards
• Clean or replace corroded or loose connector terminals and ensure the connectors are fully seated
• Correct any battery, charging or earth faults that are upsetting signal voltages
• Replace the engine control module if its torque signal output is confirmed faulty, then have it programmed to the vehicle
• Replace the transmission control module if the input is confirmed faulty and the wiring and the engine module are good

Can I keep driving?

This code for other makes

• P1894CadillacEngine Torque Signal High Voltage
• P1894ChevroletEngine 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

• P1893BuickEngine Torque Signal Low Voltage
• P1895BuickTCM To ECM Torque Reduction Circuit