Error Code P0612 is defined as Fuel Injector Control Module Relay Control, meaning there’s a problem with the fuel injector control module, often caused by bad fuel injection relay or fuse, or problems with the electrical connection.

This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, particularly those made since 1996 up to present. It commonly applies among Chevrolet, Dodge, GMC, and RAM vehicles. Specifications on the definition, troubleshooting and repairs, of course, vary from one make and model to another.

If Error Code P0612 is stored, that means the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has determined a malfunction in the internal control module. This problem is related to the part of the PCM that controls the fuel injector control module relay.

In some cases, the fuel injector controller may be separate from the PCM. Most likely, it’s integrated into the PCM, saving space, time, and money.

Also, the fuel injector control module relay may be an important part of the PCM or may be a conventional relay located away from the PCM. Thus, it’s important to consult with your reliable source of vehicle information to determine the location of the fuel injector control relay for the vehicle in question.

Every time the ignition and the PCM are powered up, multiple controllers perform self-tests. Aside from running internal controller self-tests, the CAN (controller area network) also compares signals from each module to ensure different controllers are working and interacting properly.

If the PCM detects a problem in the monitoring fuel injector relay control function, then Error Code P0612 will be stored, and simultaneously illuminate the Check Engine light. For some cases, depending on the severity of the condition, it may require multiple cycles for the Check Engine light to activate.

Common Symptoms

Depending on the severity of the problem, this code could result in a number of symptoms, especially drivability issues. Common symptoms include:

  • The vehicle having difficulty shifting (for automatic transmission)
  • Engine stalls
  • Engine vibrates when sitting idle
  • Poor acceleration
  • Increase in fuel consumption

Possible Causes

Common causes for this code include:

  • Damaged fuel injection relay/fuse
  • Malfunctioning fuel injector control module
  • Poor electrical connection
  • Busted ground wire
  • Loose control module strap
  • Corroded, shorted, or open connector or wiring in the CAN bus harness
  • Defective CAN bus

How to Check

This code is one of the many tricky codes to diagnose and fix, even with professional technicians. Also, reprogramming issue must also be considered. Without the right reprogramming equipment, it will be impossible to replace a defective controller and complete the repair.

If there are other ECM/PCM codes present, then they must be addressed first before diagnosing P0162.

Start the diagnosis by connecting the OBD-II scanner, read the codes stored in the PCM and see if there are any related codes that may be the root of the problem. After reading all saved codes, do a visual inspection of all circuits and wirings. Check the connectors and wirings using an ohmmeter to ensure there is no open or short circuit.

Then, check the PCM, CAN bus, and other relevant components.

When trying to diagnose this code, refer to your information source or TSB (technical service bulletin); looks for signs and symptoms parallel to the stored code. Search for the year, make, model, and engine of your vehicle. If you are able to find the right TSB, then you may get the best diagnostic information for your problem.

Use vehicle information source to obtain component locations, connector face views, connector pin-out charts, wiring diagram, and diagnostic flow chart related to your vehicle’s error code.

Then, use the DVOM to the test controller power supply fuses and relays. Next, test and replace any blown fuses as necessary. Fuses must be tested with circuit loaded.

If all fuses and relays are running well, check whether the controller related wiring and harness are in order. You may also want to check chassis and engine ground junctions. Again, use your vehicle information source to obtain ground locations as related circuits. Test ground integrity using the DVOM.

Then, check the system controllers for any signs of water, heat, or collision damage. Any controller that is damaged, especially by water, is considered defective and must be replaced.

If controller power and ground circuits are intact, then there’s a good chance the controller is defective, or there’s a programming error in the controller. Thus, controller replacement requires reprogramming. In some cases, you may want to get aftermarket reprogrammed controllers. Some vehicles and controllers require on-board reprogramming that may be done only through the dealership or a qualified shop.

How to Fix

Depending on the diagnosis, common repairs for this code include:

  • Repair or replacement of damaged, disconnected, corroded, or shorted connectors, components, and wiring
  • Repair or replacement of fuel injector
  • Disconnecting the CAN bus pins

With this code present, the drivability of the vehicle will suffer. Though it’s not necessarily dangerous, it could evolve into a bigger problem and more expensive fix, especially if you’re trying to force the vehicle to shift. It’s only a matter of time before gears get seriously damaged.