P1874

What it means

P1874 on a Buick means the transmission control module has seen a high voltage on the torque converter clutch (TCC) stator temperature switch circuit. The switch is a thermal sensor that tells the control module when the torque converter stator area is running hot, so it can adjust TCC operation to protect the transmission. The fault is set when the signal sits high outside what the module expects for the current conditions, which points to the switch, its wiring or the module itself.

Symptoms

• Check engine or service transmission light on
• TCC not applying or applying erratically, giving higher engine revs at cruise
• Poorer fuel economy on motorway runs
• Transmission running hot or a transmission overheat warning
• Torque converter shudder or unusual shift feel
• Transmission possibly held in a default or limited mode

Possible causes

• Open circuit or high resistance in the stator temperature switch signal wiringlikely
• Corroded, damaged or loose connector at the transmission or control modulelikely
• Faulty TCC stator temperature switch (stuck open or failed internally)possible
• Short to voltage on the signal wire from chafed or damaged harnesspossible
• Genuinely overheated transmission fluid caused by low fluid level, degraded fluid or heavy towingpossible
• Faulty transmission control module or poor module groundrare

How to diagnose

1. Read all stored codes and freeze frame data, noting transmission temperature, speed and TCC status when the fault set
2. Check transmission fluid level and condition, looking for a burnt smell, dark colour or debris
3. Visually inspect the wiring and connectors between the transmission and control module for chafing, corrosion, water ingress and bent pins
4. Check the signal circuit for continuity, short to voltage and short to ground using the wiring diagram for the specific model and transmission
5. Check the switch operation and resistance against the manufacturer specification, as the expected switch behaviour varies with model and transmission
6. Check module power and ground supplies and the reference voltage at the connector
7. Clear the code and road test while monitoring live data to see whether it returns and under what conditions
8. Only if wiring and the switch test good, consider the control module and check for any applicable software updates

How to fix

• Repair or replace damaged wiring and repair any short to voltage or open circuit
• Clean or replace corroded or damaged connectors and terminals
• Replace the TCC stator temperature switch if it fails testing
• Correct the fluid level or change the fluid and filter if it is degraded, and investigate the cause of any overheating
• Replace or reprogram the transmission control module only after confirming it is at fault, or if an outdated calibration is a known cause for that model

Can I keep driving?

This code for other makes

• P1874CadillacTCC Stator Temp. Switch Circuit High
• P1874ChevroletTCC Stator Temp. Switch Circuit High
• P1874GMTCC Stator Temp Switch Circuit High
• P1874GMCTCC Stator Temp Switch Circuit High
• P1874OldsmobileTCC Stator Temp Switch Circuit High
• P1874OtherTransmission Automatic Hall Effect Sensor Power Circuit Failure
• P1874SaturnTCC Stator Temp Switch Circuit High

Nearby codes

• P1873BuickTCC Stator Temp. Switch Circuit Low
• P1875Buick4WD Low Switch Circuit