P0884: TCM Power Input Signal Intermittent

What it means

The TCM detects intermittent loss of main supply voltage above a threshold count. Often caused by loose connector or relay fault.

At a glance

• Usually lights the check-engine light

How it works

The TCM depends on a steady main power supply to control shifts. P0884 sets when the module detects brief, repeated interruptions in that supply, even if voltage is normal again by the time the vehicle is checked.

Common causes

Most likely first.

1. TCM power relay intermittent
2. Power connector loose
3. Connector with intermittent contact under vibration

Symptoms

• Check engine or transmission warning light on
• Harsh, delayed, or missing shifts
• Possible limp mode (locked in one gear)
• Slipping or shuddering during gear changes

How to diagnose it

1. Save freeze-frame data and review any recorded supply-voltage changes or TCM resets around the time the fault set.
2. Inspect the TCM power connector, battery terminals, relay connections, and grounds for looseness, corrosion, or heat damage.
3. Check the TCM power relay and its socket for intermittent contact, then compare relay operation with the manufacturer's diagnostic procedure.
4. Monitor TCM input voltage while gently moving the harness and connectors to find vibration-sensitive interruptions.
5. If the interruption persists, test the power feed and ground under load to locate an intermittent open or high-resistance connection.

Common fixes

• Reseat and secure the TCM power connector and relay.
• Clean or replace corroded relay-socket or connector terminals.
• Replace a faulty TCM power relay.
• Repair intermittent power or ground wiring and secure it against vibration.

Can I keep driving?

Limit driving if the transmission warning appears or shifts become unpredictable, and stop safely if the vehicle loses normal shift control. Brief power interruptions can reset the TCM and cause the fault to recur without warning.