P0890 — TCM Power Relay Sense Circuit Low

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P0890 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the TCM power relay sense for damage, corrosion, chafing or poor contact.
Subsystem check Check for supply voltage at the TCM power relay sense connector first; then measure resistance from the signal wire to ground — near-zero ohms confirms a short to ground in the harness.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P0890 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P0890 (parts and labor, USD, independent shop rates): Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250; Replace the faulty sensor or actuator: $150–$500. Overall, fixing P0890 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What does OBD2 code P0890 mean?

TCM Power Relay Sense Circuit Low (P0890): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit, corroded, loose or damaged connector.

How much does it cost to fix P0890?

Control module repair — $300–$1,000; Repair wiring or connectors — $80–$250; Replace the faulty sensor or actuator — $150–$500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What are the symptoms of P0890?

Drivers most often notice: the affected system operates intermittently or not at all, Check Engine Light on, increased fuel consumption in some cases, possible limp mode depending on the affected component.

Is it safe to drive with P0890?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How do I diagnose P0890 myself?

Start with a scan: confirm P0890, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the TCM power relay sense, and verify the suspect component against live data before buying parts.

The transmission control module (TCM) manages shift points, line pressure, and torque converter clutch engagement by constantly monitoring the electrical circuits that feed it. P0890 fires when the TCM detects that the voltage on its power relay sense circuit has dropped below the acceptable threshold — essentially reading near ground potential when it should see a healthy reference voltage. This falls under the powertrain fault family in the OBD2 standard, which groups engine and transmission anomalies together under a single diagnostic umbrella.

When the sense circuit sits at an abnormally low voltage, the TCM cannot reliably confirm that its power supply relay is engaged and functioning. The module does not log P0890 after a single anomalous reading; instead, it waits for the condition to persist across repeated ignition cycles under specific load, speed, and temperature conditions. Once the threshold is crossed, the stored fault code activates the Check Engine Light and captures a freeze frame snapshot — engine load, RPM, coolant temperature, and vehicle speed at the moment of failure — which becomes the roadmap for your diagnostic session.

The underlying culprits typically involve either a direct short to ground somewhere in the wiring, a chafed harness insulation rubbing against metal, a corroded or loose connector, a power relay that has failed closed, or in rarer cases an internal driver fault inside the TCM itself. Because the code points specifically to the sense circuit rather than the main power feed, troubleshooting must focus on that particular wiring path rather than blanket replacing transmission components.

Common Symptoms of P0890

The transmission may behave erratically or fail to shift properly while P0890 is active, since the TCM cannot trust its own power supply confirmation. The Check Engine Light will illuminate once the fault meets the OBD2 trip threshold, and some vehicles experience a noticeable spike in fuel consumption because the transmission stays in a default or limp-hold gear ratio. In certain applications, the TCM may force the transmission into limp mode, limiting gears to protect drivetrain components until the fault clears. Depending on which circuit feeds into the affected relay sense line, auxiliary systems such as shift paddles or adaptive shift schedules may also go dark. The severity of symptoms varies widely — some drivers report no driveability issues whatsoever, while others lose specific transmission functions entirely.

What Triggers P0890?

A failed TCM power relay that no longer provides the expected reference voltage will pull the sense circuit low. Missing supply voltage at the relay coil or contacts produces the same effect. Wiring that has been chafed or pinched will short the signal line to ground, collapsing the voltage reading. A weak or corroded ground connection somewhere in the relay control circuit prevents proper voltage pull-up. Oxidation, bent pins, or moisture intrusion at the TCM harness connector degrade signal integrity. The TCM itself can develop an internal driver fault that forces the sense input low regardless of external wiring condition. Finally, an open circuit anywhere between the relay and the TCM sense input can manifest as a phantom low condition during vibration or thermal cycling.

How to Diagnose P0890

Start by connecting a scan tool and verifying that P0890 is present in the transmission or powertrain control module, then record the freeze frame data for reference during your road test. Address any other stored codes first — related electrical faults often cascade and mask the root cause, so resolving secondary codes early prevents chasing ghost problems. Consult manufacturer TSBs for your specific make, model, and model year; some P0890 failures have documented factory remedies or calibration updates that resolve the issue without physical repair. Perform a thorough visual inspection of the TCM power relay wiring harness, looking for worn insulation, rub points against brackets, and any sign of moisture or corrosion at connectors. Measure supply voltage at the relay first, then check the resistance from the sense circuit wire to chassis ground — a reading below one ohm confirms an unwanted short to ground in the harness. Test the actual component connector for proper reference voltage, ground continuity, and signal integrity. Use a wiggle test on the harness while monitoring live data to expose intermittent opens or shorts that only appear under vibration. Clear the code and drive the vehicle through the exact conditions recorded in the freeze frame, then recheck for P0890 recurrence.

Repair Options and Costs

Always address wiring and connector issues before committing to expensive component replacement. If the short to ground is localized, cutting out the damaged section and installing a proper repair harness or soldered splice typically resolves P0890 without further intervention. When corrosion or pin damage at the TCM connector is the source, connector replacement or pin repair restores circuit integrity. The three primary repair scenarios for P0890 carry the following typical parts-and-labor price ranges at independent shops:

Wiring or connector repair: $80–$250
Sensor or actuator replacement: $150–$500
TCM or control module repair or replacement: $300–$1,000

Overall, an accurate diagnosis targeting the cheapest likely cause first typically keeps total invoice between eighty and one thousand dollars depending on what actually failed. Spending time with a multimeter before purchasing parts almost always reduces the final bill.

Can You Still Drive?

P0890 carries a short-term driving-safety rating, meaning most vehicles remain operational after the code sets. You may notice reduced performance, elevated fuel consumption, or the loss of one or two transmission functions, but the car should still move under its own power. That said, if the fault causes intermittent stalling, a no-start condition, or triggers stability or braking warnings, the situation becomes urgent and the vehicle should be towed rather than driven. Until you confirm the exact cause, treat P0890 as a "drive to the shop" issue rather than an open-the-hood-and-ignore-it one.