P0890

P0890 is a TCM power relay sense circuit low fault, meaning the transmission control module is reading a low voltage on the feedback line that should be receiving battery voltage when the relay is energized. Cheapest first: this code is fundamentally an electrical supply problem to the TCM, so start with the basics: load-test the battery (must hold above 9.6V during a 15-second cranking load) and clean the battery terminals and the engine-to-chassis and battery-to-chassis ground straps. Locate the TCM power relay in the underhood fuse box and swap it with an identical relay; if the code clears, the relay was the issue. If the relay is good, back-probe the relay sense wire at the TCM connector with KOEO and the relay commanded on, and verify battery voltage. Caveat: replacing a TCM (often $800 to $2,000 new and requiring programming) on a P0890 without verifying the relay, the relay socket, and the power and ground feeds first is one of the most common transmission-shop misdiagnoses.

Vehicle-specific patterns: 2002 to 2008 Dodge Ram 1500, 2500, and 3500 with the 45RFE, 545RFE, or 48RE transmissions set P0890 from the TIPM (totally integrated power module) internal relay failing, a documented Chrysler defect with a class action involved. 2007 to 2014 Chrysler 300, Dodge Charger, and Magnum with the W5A580 (Mercedes 5G-Tronic) trip P0890 from the same TIPM relay pattern. 2004 to 2010 Ford F-150 with the 4R75E sets P0890 when the underhood power distribution box gets water intrusion from the cowl drain. 2008 to 2012 Jeep Liberty and Grand Cherokee with the 545RFE share the Chrysler TIPM failure pattern. Estimated repair: $80 to $1,300.