Error Code P0615 is defined as Starter Relay Circuit. 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. This includes, but not limited to vehicles from manufacturers like Acura, Buick, Cadillac, Chevrolet, GMC, Honda, Infiniti, and Peugeot. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

The job of the Starter Relay Circuit is to provide a power source to the starter to crank and start the engine. Depending on the specific vehicle and its drivetrain configuration, there can be multiple components involved in this process. It starts at the battery, includes ignition switch, fuses, starter solenoid, starter relay, and multiple safety devices, such as clutch position sensor and the neutral safety switches.

Error Code P0615 is associated with the Starter Relay Circuit, which in most circumstances, causes the vehicle not to start. This code happens when the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) sees a malfunction within the starter relay circuit (also referred as Ignition Switch Circuit in other vehicle makes). Many codes can be set when the PCM detects improper signals within the starter relay circuit, based on their specific malfunction.

Other related codes include:

Common Symptoms

There will be no drivability symptoms for this code. Aside from illuminating the Check Engine light and registering the code, common symptoms for this problem include:

  • Engine no start condition
  • Sporadic no-crank occurrences

Possible Causes

There are many reasons for this code to appear, the most common causes are:

  • Defective ignition switch
  • Blown fuse
  • Defective starter
  • Bad starter relay
  • Shorted or open starter relay circuit
  • Damaged or defective battery cable(s)
  • Defective starter motor or solenoid
  • Corroded or damaged connector
  • Defective PCM (rare)

How to Check

As with most diagnosis, the first step for troubleshooting this code is to research it with the TSB (Technical Service Bulletins) for the specific year, model, and power plant. This usually provides the best solution.

Next is to consult with the specific tech data for the vehicle and see if a fuse is incorporated into the starter relay circuit, and check whether it’s blown if applicable. If the fuse is in good shape, then find all components associated with the starter relay circuit and check for obvious signs of damage.

Then, perform a thorough visual inspection and check all associated wirings for obvious signs of damage, such as bare wires caused by running, scraping, or burnt spots.

Next, check the connectors and connections for security; look for signs of corrosion and damaged pins. The whole process should include all wiring connectors and connections to the battery, PCM, ignition switch, starter, starter relay, and starter solenoid.

Advanced Steps

Advanced steps for diagnosis vary from one vehicle to another and may require specific advanced equipment and tools, such as a digital multi-meter, and specific technical references for the vehicle. Voltage requirements also vary based on specific year and model of the vehicle.

Voltage Checks

Battery voltage should be around 12V, and the starter should have battery voltage with the ignition switch in the start position. The presence of voltage with the starter not engaging is a sign of a defective starter or starter solenoid. The lack of voltage means the ignition switch is faulty, or there’s a problem with the wiring.

If this process determines the absence of a power source or ground, then perform a continuity test to check the integrity of the wiring, ignition switch, and other components. Continuity test must be performed with the power removed from the circuit while reading for wiring and connections must be at 0 ohms of resistance, unless otherwise specified in the technical data of the vehicle. Resistance or no continuity means there’s a faulty wiring problem (open or short) and must be repaired or replaced.

How to Fix

Depending on the diagnosis, repairs for this code include:

  • Replacement of blown fuse
  • Replacement of damaged battery cables
  • Repair or replacement of defective starter relay
  • Repair or replacement of faulty wirings or damaged connectors
  • Replacement of ignition switch
  • Replacement of the starter motor or solenoid (rare)
  • Flashing or replacement or reprogramming of PCM (rare)

The most common mistake when addressing this code is replacing the starter or PCM when the damage is in the wiring or other components. Thus, it’s extremely important to conduct a thorough diagnosis before replacing anything to avoid unnecessary replacements of parts.