P0890 code definition
Applying only to vehicles with a traction control system, a P0890 trouble code indicates a fault in the traction control module communication circuit. The traction control module communication circuit relays information to the Powertrain Control Module (PCM) that helps the vehicle computer decide on how much fuel and RPMs the vehicle engine needs depending on current driving conditions and factors. The traction control module communication circuit also helps with engine timing and other things while the vehicle is in operation. Some similar trouble codes include P0880, P0881, P0882, P0883, P0884, P0885, P0886, P0887, P0888, P0889, P0891, and P0892 codes.
What the P0890 code means
When the PCM or other control modules do not receive the necessary data from the traction control module communication circuit, a P0890 trouble code is stored and the Check Engine light may illuminate, in addition to the traction control malfunction light illuminating. The PCM might also place the vehicle transmission into Limp-in mode.
What causes the P0890 code?
A defective traction control ON/OFF switch is the most common cause of a P0890 trouble code, with liquid spilled into the switch being the most likely culprit behind the failure. Some other causes include shorted, corroded, and damaged wiring or connectors, as well as corrosion in the sensor connector.
What are the symptoms of the P0890 code?
In addition to a stored code and illuminated Check Engine and Traction Control Malfunction lights, some other symptoms of a P0890 trouble code include a lack of traction while driving in slippery conditions and failure of the traction control system. Other symptoms include harsh shifting or failure to shift by the transmission, as well as a reduction in the fuel efficiency of the vehicle.
How does a mechanic diagnose the P0890 code?
To properly diagnose a P0890 trouble code, a mechanic needs an advanced scanner, digital volt/ohmmeter, a specialized scanner for diagnosing the pins of the Controller Area Network (CAN) Bus harness, auxiliary ground cable, and a CAN Bus system wiring diagram. The mechanic must also perform the following steps when diagnosing:
- Inspect and check the wiring and connectors for damage or fault.
- Clear the trouble code and test the system to see if it returns.
- The mechanic should also download all stored codes and any flash frame data.
- If the code returns, the mechanic needs to use a specialized scanner to test the pin values of the CAN Bus Harness, comparing their findings with the manufacturer's specifications.
- When inspecting and testing the CAN Bus system pins, the mechanic should use both a CAN Bus system wiring diagram and an auxiliary ground cable to make the process easier.
- The mechanic should also check the continuity of the ground circuits of the various related control modules using the digital volt/ohmmeter.
- Clear the code and retest the system to see if the trouble code returns.
Common mistakes when diagnosing the P0890 code
When diagnosing a P0890 trouble code, mechanics often make the mistake of citing the traction control module as the problem instead a faulty switch, wiring, or connector, which is actually at fault. This results in the problem remaining unfixed and the trouble code returning.
How serious is the P0890 code?
A P0890 trouble code needs to be dealt with as soon as possible. The resulting symptoms make the vehicle difficult to drive at best. Some of the problems associated with a P0890 trouble code include loss of traction, failure of the transmission to shift properly, and worsening fuel mileage.
What repairs can fix the P0890 code?
Repairing a P0890 trouble code requires a mechanic to do the following:
If replacing wiring in the CAN Bus harness, the mechanic might be better served replacing the whole harness as opposed to individual wires.
Replace any faulty control modules, including the traction control module if faulty.
Need help with a P0890 code?
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This article originally appeared on YourMechanic.com as P0890 OBD-II Trouble Code: Traction Control Module (TCM) Power Relay Sense Circuit Low and was authored by Cheryl Knight.