Fuel Injector Control Module Relay Control
Code P0612 indicates the PCM has detected a problem with the relay control circuit that supplies power to the fuel injector control module or other critical control circuits. This prevents proper operation of engine control systems and can cause significant drivability issues.
What You Might Notice
- Engine drivability issues or rough running
- Reduced engine performance or power loss
- Diminished fuel efficiency
- Engine may stall or have difficulty starting
- Check engine light illuminated
Most Common Causes
- 1
Defective PCM Power Supply Relay
The relay controlling power to the PCM or fuel injector control module has failed or is not switching properly. This is the most common cause of this code.
- 2
Open or Shorted CAN/Control Harness
Wiring connections between the relay, PCM, and control modules are damaged, corroded, or disconnected, preventing proper power distribution.
- 3
Faulty PCM or Programming Error
The powertrain control module itself is defective or has lost its programming, preventing it from controlling the relay circuit correctly.
- 4
Insufficient PCM Ground or Power Source
A poor ground connection or failed main power feed to the PCM prevents the relay from receiving proper control signals.
How to Diagnose It
- 1
Check Defective PCM Power Supply Relay — The relay controlling power to the PCM or fuel injector control module has failed or is not switching properly. This is the most common cause of this code.
- 2
Check Open or Shorted CAN/Control Harness — Wiring connections between the relay, PCM, and control modules are damaged, corroded, or disconnected, preventing proper power distribution.
- 3
Check Faulty PCM or Programming Error — The powertrain control module itself is defective or has lost its programming, preventing it from controlling the relay circuit correctly.
- 4
Check Insufficient PCM Ground or Power Source — A poor ground connection or failed main power feed to the PCM prevents the relay from receiving proper control signals.
How to Fix It
- 1
Replace PCM Power Supply Relay
Locate the fuel injector control module relay or PCM power relay in the relay box and replace it with a new relay of the correct specification.
- 2
Inspect and Repair Wiring Harness
Check all connections between the relay, PCM, and fuel injector control module for corrosion, loose terminals, or damaged wires. Clean connectors and repair or replace damaged harness sections.
- 3
Check PCM Ground and Power Connections
Verify the main power and ground cables to the PCM are secure and in good condition. Clean corroded terminals and tighten all connections.
- 4
Reprogram or Replace PCM
If relay and wiring are confirmed good, the PCM may require reprogramming or replacement if it has lost its calibration or is defective.
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