Skip the auto shop - Our mechanics make house calls

P0888 OBD-II Trouble Code: Transmission Relay Sense Circuit (or Relay Output Always Off)

check engine light

P0888 code definition

The P0888 code is the universal code for Transmission Relay Sense Circuit (or Relay Output Always Off). Co-occurring or alternative codes may be P0869, P0871, P0876, or any of P0885 – P0892.

What the P0888 code means

P0888 is the OBD-II trouble code indicating a problem with the transmission control relay or else somewhere in the related circuitry. The transmission control relay supplies power to the solenoid pack when the transmission is functioning properly. This code is thrown when fewer than three volts are present at the transmission control relay output terminals of the PCM (powertrain control module) as the PCM is energizing the relay.

What causes the P0888 code?

A transmission control power relay sense circuit problem can be caused by a number of malfunctions:

  • A faulty TCR (transmission control relay)
  • An open TCR output circuit
  • A short in the TCR control or output circuit
  • A faulty PCM (powertrain control module)
  • A faulty connection within the circuit
  • A faulty transmission solenoid/pressure switch assembly

What are the symptoms of the P0888 code?

When a vehicle is storing this code, it will likely cause the Check Engine Light to come on, and can potentially result in the vehicle only operating in “limp” mode, failing to switch gears. Some people also experience a loss of A/C power.

How does a mechanic diagnose the P0888 code?

P0888 is diagnosed by hooking an OBD-II scanner to the vehicle’s port. The technician will then document freeze frame data, determine when the code set along with any concurring codes, and then clear the vehicle’s computer of the data and test drive it to see if the code returns.

During the road test, the mechanic should observe the sensor’s live data. If the code does return, the wiring, PCM connector, and relay contacts should be visually examined. If these are not the apparent cause of the problem, he or she may use a multimeter to test the circuit according to the manufacturer’s pinpoint tests.

Common mistakes when diagnosing the P0888 code

The most common errors when diagnosing this code occur when the proper steps are not followed to find the root of the problem. There is a temptation to simply flash the TCM or replace the TCR or transmission solenoid without making sure the voltage is correct throughout all of the involved circuitry.

How serious is the P0888 code?

This fault code can be very serious if it is causing the vehicle to operate in limp mode. Vehicles in limp mode should not be driven except to get to the nearest shop. If your vehicle shows this code, you should have a qualified technician address the problem as soon as possible to prevent further damage.

What repairs can fix the P0888 code?

The most common potential repairs to address the P0888 code are as follows:

  • Check to make sure the code returns after all codes have been cleared and the vehicle driven again.
  • Inspect the TCR to ensure it’s working and that the ground is not faulty.
  • Visually inspect all wiring and connectors.
  • Ensure that there is no 12-volt signal at the transmission control module, indicating an open circuit.
  • Inspect input and output sensors for dirt and grime. Use contact cleaner if necessary.
  • Replace TCR if necessary.
  • Replace TCR harness if necessary.
  • Replace transmission solenoid/pressure switch assembly if necessary.

Additional comments for consideration regarding the P0888 code

Identifying and repairing P0888 can be a very complex, involved repair which is beyond the scope of most home mechanics. Advanced electrical skill is generally required, and the ability to examine multiple small, specific parts, as there are several possible causes, most requiring testing of voltage between certain components. If possible, it’s best to have a trained automotive technician diagnose and fix this code as soon as you notice a problem.

Need help with a P0888 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222...


Related questions

Q: Car is misfiring and has a lack of power

It is very difficult to definitively say what the issue is. Have you had the vehicle scanned for diagnostic troubleshooting codes? If not, you should start there. Due to your vehicle being pre-1996, the method of receiving codes will be...

Q: Limp mode was on and I turned off the car. Now limp mode is off but the Check Engine Light is on.

When the car goes into limp mode, generally the reason for this is related to a critical component or sensor detecting a problem that may cause serious damage. There are existing codes in the computer which have been registered as...

Q: will a temperture switch cause an engine not to start?

The engine coolant temperature sensor sill not cause the engine to die or not start, but can cause the fuel system to go full rich. The engine dies when getting hot is most likely due to an ignition spark loss...