P0885Generic code

P0885 Code: TCM Power Relay Control Circuit/Open

The P0885 code means the control circuit of the transmission control module (TCM) power supply is open, so the component gets no current when it is commanded on. It can cause limp mode or erratic shifting. A disconnected connector, an open coil or a cut wire is the usual cause.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$10 to $400
Difficulty
Medium
System
Transmission
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0885 code means

The transmission computer needs a stable power supply. Some vehicles feed it through a relay that the module itself controls, and others feed it straight from the fuse box. The module monitors its own supply voltage.

The computer watches the control circuit from its own driver transistor. The P0885 code indicates an open circuit: the component gets no current when it is commanded on. Before replacing the component, check the fuse, relay, connector and wiring, since they are the most common cause.

With low or unstable voltage, the transmission shifts erratically or goes into limp mode, and solenoid codes can show up even though the solenoids are fine. Check the battery, alternator, fuses and grounds before anything else.

Measure the component resistance at its connector: if it is infinite, it is open inside. If it reads correctly, follow the control wire to the computer looking for a break, especially in the sections near the exhaust or at intermediate connectors.

P0885 code symptoms

  • Check engine light or another warning light on.
  • Transmission in limp mode or shifting erratically.
  • Erratic shifts.
  • Limp mode.
  • Several transmission codes at the same time.

Likely causes of the P0885 code

  1. Disconnected connector or one with a broken lock.
  2. Open coil, with infinite resistance.
  3. Cut wire. Check the areas where the harness rubs.
  4. Blown fuse, often because of an earlier short.

How to diagnose the P0885 code step by step

  1. Activate the component with the scan tool and see whether it responds.
  2. Check the fuse and relay. Measure voltage on both sides of the fuse, and swap the relay with an identical one.
  3. Measure the supply at the connector: battery voltage with the key on or when the component is activated.
  4. Measure the component resistance and compare it with the manual, and also the insulation to ground.
  5. Check the control wire for continuity to the computer and for the absence of shorts.
  6. Measure battery and charging voltage.
  7. Measure the voltage drop on the module grounds, which should be under 0.2 V.

How to fix the P0885 code

  • Repair the connector, the wiring or the power supply.
  • Replace the transmission computer power supply component if it does not respond with correct power and control.
  • Clear the codes and verify.

Technical reference data

  • Supply voltage: battery voltage (13.5 to 14.7 V with the engine running).
  • Reference values are only a guide, so look up the manufacturer data for your vehicle.
  • Ground voltage drop under load: below 0.2 V.

Brand-specific notes

If a P0885 code shows up together with other transmission codes, suspect the power supply and grounds before you suspect the individual parts, since a weak supply makes healthy solenoids look bad.

P0885 on Chrysler

On many Chrysler vehicles the transmission relay is in the fuse box in the engine compartment.

P0885 on Ford

On many Ford vehicles the transmission relay is in the fuse box in the engine compartment.

Frequently asked questions about P0885

Can I drive with a P0885 code?
Yes, with caution. The transmission may shift erratically or drop into limp mode, so get it checked before long trips.
What does the transmission computer power supply do?
The transmission computer needs a stable supply. Some vehicles feed it through a relay it controls, and others straight from the fuse box. The module monitors its own supply voltage.
Does the part always have to be replaced?
No. Check the fuses, relays, connectors and wiring first.
How much does it cost to fix P0885?
Roughly $10 to $400, from a fuse or relay up to a wiring repair or a new part.
What does the P0885 code mean?
It is a generic OBD2 code that means the control circuit of the transmission control module power supply is open.

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