TCM Power Relay Control Circuit Low
P0886 indicates the TCM (Transmission Control Module) power relay control circuit is detecting low voltage. The PCM has detected insufficient voltage supply to the transmission control module, which prevents proper transmission operation and engagement of electronic systems.
What You Might Notice
- Check Engine Light (MIL) illuminated
- Transmission shifts erratically or does not shift properly
- Electronic traction control disabled or inoperative
- Reduced power or limp mode activation
- ABS system disabled or inoperative
Most Common Causes
- 1
Blown TCM power relay fuse
A blown fuse in the TCM power relay circuit prevents adequate voltage from reaching the transmission control module. This is the most common cause and easiest to diagnose.
- 2
Faulty TCM power relay
A malfunctioning relay fails to supply consistent voltage to the TCM. The relay may be stuck open, corroded, or internally damaged, cutting power to the module.
- 3
Corroded or loose battery connections
Poor battery terminal connections or corroded ground cables reduce available voltage throughout the electrical system, including the TCM circuit. This causes insufficient voltage delivery.
- 4
Wiring harness damage or disconnection
Damaged, corroded, or disconnected wires in the TCM power supply circuit prevent proper voltage delivery. Water intrusion or rodent damage can compromise wire integrity.
How to Diagnose It
- 1
Check Blown TCM power relay fuse — A blown fuse in the TCM power relay circuit prevents adequate voltage from reaching the transmission control module. This is the most common cause and easiest to diagnose.
- 2
Check Faulty TCM power relay — A malfunctioning relay fails to supply consistent voltage to the TCM. The relay may be stuck open, corroded, or internally damaged, cutting power to the module.
- 3
Check Corroded or loose battery connections — Poor battery terminal connections or corroded ground cables reduce available voltage throughout the electrical system, including the TCM circuit. This causes insufficient voltage delivery.
- 4
Check Wiring harness damage or disconnection — Damaged, corroded, or disconnected wires in the TCM power supply circuit prevent proper voltage delivery. Water intrusion or rodent damage can compromise wire integrity.
How to Fix It
- 1
Inspect and replace TCM power fuse
Locate the TCM power fuse in the engine bay fuse box using the owner's manual or service guide. Test the fuse for continuity and replace with the correct amperage rating if blown. Verify no short circuit exists before reinstalling.
- 2
Test and replace TCM power relay
Use a multimeter to test the relay for proper operation. If the relay does not click when powered or fails continuity tests, remove it from the fuse box and install a new relay of the same specifications.
- 3
Clean and secure battery connections
Disconnect the negative battery terminal and inspect both battery terminal connectors for corrosion. Clean with a wire brush and reconnect securely. Also inspect ground cable connections to the engine block and chassis for looseness or corrosion.
- 4
Inspect TCM power supply wiring harness
Trace the wiring from the TCM connector and relay back to the fuse box, looking for damaged insulation, loose connections, or corroded terminals. Repair or replace compromised sections of the harness and reseat all connectors firmly.
Need a deeper diagnosis?
Search for related repair guides or browse by system.