01 5 Things You Should Know About Oxygen Sensors in Cars • 02 CAN Bus in Cars: Everything You Need to Know • 03 The Secret Role Of Oxygen Sensors And How They Quietly Wast… • 04 Mastering Overdrive: A Guide to Efficiency in Automatic Tra… • 05 Understanding Your Mass Airflow Sensor: Function & Benefits… • 06 The Best Engines That Should Have Been in Sports Cars But W… • 07 U0009 High Speed CAN Communication Bus (-) shorted to Bus (… • 08 The Reason Fault Codes Change After Driving For A While • 09 When Should the Oxygen Sensor Be Replaced? A Comprehensive • 10 The Single Component Under Your Hood That Could Be Draining… •

DTC codes / P08xx · Transmission / P0890

P0890TCM Power Relay Sense Circuit Low

P0890 indicates that the transmission control module (TCM) has detected a low voltage condition on the power relay sense circuit, which is the feedback line that confirms the relay is supplying power to the TCM. The TCM expects to see battery voltage on this circuit when the relay is commanded on, but instead it sees a voltage below the threshold, indicating a problem with the relay, its control circuit, or the wiring.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (MIL) on the dashboard.
  • Transmission may enter limp mode, limiting gear selection or shifting harshly.
  • Erratic or delayed shifting, or failure to shift at all.
  • The engine may crank but not start if the TCM is not powered.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.

Common causes, most likely first

  1. Faulty transmission control module (TCM) power relay, such as burned contacts or a stuck open coil.
  2. Blown fuse or fusible link supplying power to the relay or TCM.
  3. Corroded, loose, or damaged wiring or connectors in the relay sense circuit.
  4. Poor ground connection for the relay or TCM, causing voltage drop.
  5. Internal fault in the TCM causing it to misread the sense circuit voltage.
  6. Water intrusion or physical damage to the wiring harness or relay box.

How to diagnose and fix it

  1. Verify the battery is fully charged and in good condition, as low system voltage can set this code.
  2. Check all fuses and relays related to the TCM power supply, replacing any that are blown or suspect.
  3. Inspect the relay and its socket for corrosion, tightness, and signs of overheating; test the relay with a multimeter or swap with a known-good relay of the same type.
  4. Measure voltage at the TCM power relay sense circuit with a multimeter, comparing to battery voltage; check for excessive voltage drop across the relay contacts and wiring.
  5. Perform a voltage drop test on the ground circuit for the TCM and relay to ensure a clean, low-resistance path to the battery negative.
  6. Inspect the wiring harness for chafing, corrosion, or loose pins, especially at connectors between the relay, fuse box, and TCM.
  7. If all external circuits and components test good, follow the manufacturer's diagnostic flow chart for the TCM, which may involve checking for internal faults or reprogramming/replacing the TCM.

Relay Sense Circuit Checks Before TCM Replacement

  • A weak or failing battery or charging system can cause this code because the TCM may not see enough voltage on the sense circuit during cranking or low-rpm operation.
  • The relay sense circuit is often confused with the relay control circuit; the sense circuit is a feedback line, so a fault here does not always mean the relay itself is bad.
  • Corrosion inside the underhood fuse box or relay center is a common hidden cause, especially in vehicles exposed to road salt or humid climates.
  • After repairing the fault, the code may require several drive cycles to clear, and some vehicles need the TCM to relearn adaptive shift strategies.
  • A faulty ignition switch or main power supply to the fuse box can mimic a relay sense circuit failure, so always verify power and ground at the fuse box first.

Can I keep driving with P0890?

If the vehicle drives normally with only the warning light on, you can drive it to a repair shop, but avoid long trips or heavy loads. If the transmission is in limp mode or shifting erratically, limit driving to a short distance to a safe location and arrange for a tow to prevent further damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage