Technical Description of OBD-II Trouble Code
Control of Fuel Injector Module Relay
What does that signify?
This generic powertrain diagnostic trouble code (DTC) is commonly found in many OBD-II vehicles, including Chevrolet, GMC, Dodge, Ram, and others.
A stored code P0612 indicates an internal malfunction in the powertrain control module (PCM). The issue is related to the PCM’s control of the fuel injector control module relay.
In some cases, the fuel injector controller may be separate from the PCM, but it is usually integrated into the PCM to save space, time, and money for automakers.
Similarly, the fuel injector control module relay may be part of the PCM or a separate conventional relay located away from the PCM. To determine the location of the fuel injector control relay for a specific vehicle, consult a reliable source of vehicle information.
Every time the ignition is turned on and the PCM is energized, multiple self-tests are performed by the controllers. The controller area network (CAN) is used to compare signals from each module to ensure proper interaction between the controllers.
If the PCM detects a problem in the fuel injector relay control function, it will store a code P0612 and may illuminate the malfunction indicator lamp (MIL). Depending on the severity of the malfunction, multiple failure cycles may be required for MIL illumination.
A fuel pump control module:
What is the seriousness of this DTC?
Internal control module codes should always be taken seriously. A stored code P0612 could result in various drivability concerns, including a no-start condition.
What are some of the symptoms of the code?
Symptoms of a P0612 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P0612 troubleshooting steps?
Diagnosing a code P0612 can be challenging, even for experienced technicians. Reprogramming may also be an issue, as it requires the necessary equipment. Before attempting to diagnose a P0612, any ECM/PCM power supply codes present should be repaired.
There are several preliminary tests that can be performed before determining if a controller is defective. These tests require a diagnostic scanner, a digital volt/ohmmeter (DVOM), and reliable vehicle information.
Connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. Record this information in case the code is intermittent. After recording the information, clear the codes and test drive the vehicle until the code is reset or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more difficult to diagnose. If the code is reset, continue with the following preliminary tests.
When diagnosing a P0612, information is crucial. Search for technical service bulletins (TSB) that match the stored code, vehicle information (year, make, model, and engine), and exhibited symptoms. The right TSB may provide diagnostic information that can greatly assist in the diagnosis.
Use the vehicle information source to obtain connector face views, connector pin-out charts, component locators, wiring diagrams, and diagnostic flow charts related to the code and vehicle in question.
Use the DVOM to test controller power supply fuses and relays. Pay special attention to the fuel injector controller relay if it is an external relay. Follow the manufacturer’s recommendations for testing the relay with the DVOM. If the fuel injector control relay is faulty and integrated with the PCM, the PCM must be replaced and reprogrammed. Replace blown fuses as necessary, testing them with the circuit loaded.
If all fuses and relays appear to be functioning correctly, visually inspect the wiring and harnesses related to the controller. Also check the chassis and engine ground junctions. Use the vehicle information source to obtain ground locations for the relevant circuits. Use the DVOM to test ground integrity.
Inspect system controllers for signs of water, heat, or collision damage. Any damaged controller, especially due to water, should be considered defective.
If the controller power and ground circuits are intact, suspect a defective controller or a controller programming error. Controller replacement will require reprogramming. Aftermarket sources may offer reprogrammed controllers for some vehicles, while others may require on-board reprogramming that can only be done through a dealership or qualified source.
