We had an interesting case about a month ago. I received a call from a shop that had a 2013 Toyota RAV4 with a 2.5-litre engine that would not shut off. The only way to get the engine to shut off was to remove the battery cable which caused the vehicle to quit immediately. I thought I might be able to help the shop solve the problem without actually having to go to the vehicle, so I opted to do a remote diagnosis and had the shop technician carry out the physical testing.

Initial scan results

A scan was performed on the vehicle and the following codes were retrieved, C1551, B1660, U0129, U0131 and B1507. The ‘U” codes were for no communication with the ABS and Power Steering modules while the C1551 was a Power Steering B+ fault and the B1660 and B1507 were codes for the ABS light circuit and a turn signal fault respectively. None of the codes seemed to have anything to do with the engine not shutting off so they were ignored.

As a general rule, is that when a battery is disconnected, the vehicle should stay running as the alternator would be supplying power to run it. Another general rule is that modern engine computers require an ignition input to turn on and off. Since the vehicle shut off when the battery cable was removed, this indicated to me that the RAV or portions of the vehicle were turning off when the ignition switch was turned to off. The alternator has an ignition feed that turns it on and off. The fact that the engine quit when the battery was disconnected indicated that the alternator was being turned off. Without disconnecting the battery however, the car would continue to run even with the key turned off.

PCM power inputs

The next obvious step was to check the Power inputs to the PCM and to see if they were turning off with the ignition switch. This was straight forward; you just need to go to the wiring diagram and examine the PCM power and ground circuits and see which circuits turned off with the key.

After a bit of digging, we learned that PCM was powered up through a fuse in the IGN in the instrument panel fuse block. When the fuse was pulled the engine quit. From this we determined that the PCM ignition circuit was staying powered up when the car was being shut off. Next step was to trace power on the circuit back to its source. Following the wiring diagram, we traced power back to the IG2 relay in the under-hood fuse block.

Remote start issue

The relay is turned on directly from the ignition switch. This led us to pic 3 of the ignition switch which powers the IG2 relay. The Ignition switch connector was disconnected, and we measured the circuit on the harness side. The circuit should be dead as it is disconnected from its power source. However, we measured battery voltage on the circuit. The only way this can happen of there is something feeding power into the circuit such as an aftermarket device, corrosion in a connector or wires chafed together somewhere in the harness. Time to start looking for the culprit. It didn’t take very long. Tracing the wire from the ignition switch we found an aftermarket remote start wired into the circuit. The remote start module was removed, and the problem went away.

Did I mention that I do not like aftermarket devices? The final solution was to completely remove the aftermarket remote start which returned the vehicle to normal operation.