P0887 — TCM Power Relay Control Circuit High

How do I diagnose P0887 myself?

Start with a scan: confirm P0887, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the TCM power relay control, and verify the suspect component against live data before buying parts.

What are the symptoms of P0887?

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

Will P0887 clear itself?

Sometimes P0887 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What does OBD2 code P0887 mean?

P0887 — TCM Power Relay Control Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: blown fuse feeding the circuit, poor ground connection, open or shorted wiring in the circuit.

Is it safe to drive with P0887?

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.

When the transmission control module needs to manage gear shifts and internal functions, it relies on a dedicated power relay to deliver consistent voltage. Code P0887 triggers when the control circuit feeding that relay shows a voltage reading that sits higher than it should — essentially the opposite of what the module expects to see. The powertrain control module continuously monitors this circuit, and once it detects the abnormal reading across multiple drive cycles, it locks the fault into memory and illuminates the check engine light.

The term "circuit high" in P0887 indicates the signal line is carrying near battery voltage when it should be grounded or at a lower reference level. This condition typically stems from a short to a power source somewhere in the wiring, a failed component pulling the line high, or a broken ground path that leaves the circuit floating at elevated voltage. Freeze frame data stored alongside the code captures the exact operating conditions — engine speed, load percentage, coolant temperature, and vehicle speed — giving a technician a precise snapshot of when the malfunction first appeared.

Understanding why the TCM power relay control circuit behaves this way matters because the relay itself is the gateway for transmission operation. When its control circuit fails to toggle properly between ground and battery voltage, the module cannot reliably activate or deactivate the relay. This creates a cascade of potential issues depending on how the vehicle manufacturer programmed the fallback behavior.

Common Symptoms of P0887

• The check engine light remains illuminated after the fault cycle completes
• The transmission may shift harshly, slip, or refuse to shift entirely
• Some vehicles activate a limp-home mode that limits gears and performance
• Intermittent loss of transmission functions while driving
• In certain applications, auxiliary systems tied to the TCM relay lose power
• Fuel economy can decline noticeably when the transmission operates outside optimal parameters
• Rarely, the engine may stall or fail to start if the TCM loses primary power

What Causes P0887?

• The TCM power relay itself has failed and holds the control circuit at high voltage
• An open or corroded ground connection prevents the circuit from dropping to ground potential
• The signal wire has shorted directly to a constant power source such as battery positive
• The transmission control module internal driver circuit has burned out
• A loose, damaged, or corroded connector interrupts ground continuity
• Chafed wiring creates a short between the control circuit and a power feed
• The related sensor or actuator in the affected circuit has developed an internal short

How to Diagnose P0887

1. Connect an OBD2 scanner, retrieve code P0887, and record all freeze frame data — these parameters reveal the exact driving conditions when the fault occurred.
2. Scan for additional diagnostic trouble codes. Related transmission or sensor codes often point to the underlying cause rather than assuming the relay itself failed.
3. Consult manufacturer technical service bulletins using your vehicle's VIN. Many powertrain codes have documented factory fixes, software calibrations, or known issues specific to the make and model.
4. Perform a visual inspection of the TCM power relay harness and connectors, looking for damaged insulation, bent pins, moisture intrusion, or corrosion buildup.
5. With the relay disconnected, probe the harness control circuit: if voltage reads high with the component unplugged, the wiring itself has a short to power; if voltage drops to normal range, the relay or connected component is faulty.
6. Test ground integrity by measuring resistance from the ground pin to chassis — any value above 1 ohm warrants investigation.
7. Clear the code, recreate the freeze frame conditions during a test drive, and verify whether P0887 returns.

Repair Options for P0887

• Wiring and connector repair: $80–$250 — fixing damaged harness sections, replacing corroded terminals, or sealing moisture-damaged connectors typically resolves the issue when the fault lies in the wiring.
• Sensor or actuator replacement: $150–$500 — if testing confirms a failed component in the TCM power relay circuit, replacing the faulty part eliminates the short pulling the line high.
• Control module repair or replacement: $300–$1,000 — when internal circuitry within the TCM fails, repair through a specialist or full module replacement becomes necessary.

Total Cost to Fix P0887

Most P0887 repairs fall between $80 and $250 if the problem is wiring-related, the most common scenario. Component replacement adds $150–$500 depending on the part. Control module work represents the high end at $300–$1,000 but is rarely required as a first step. Investing in proper electrical diagnosis before purchasing parts prevents unnecessary expenses — the priciest scenario should never be assumed without verification.

Can You Drive with P0887?

The severity level for this code ranks as short-term drivable in most vehicles. The transmission may feel sluggish or restricted under limp-home mode, but the car generally remains operational. However, if symptoms progress to stalling, complete failure to start, or warning lights for braking or steering systems, treat the situation as urgent and seek immediate service.