Engine code
Q My 2007 Mazda RX-8 has a ‘check engine’ light on and is showing fault code ‘2008’. I think this translates to ‘low voltage on intake runner bank 1’ – on an RX-8, this is the auxiliary port valve drive motor circuit (basically it opens up extra ports at higher revs). It can be reset with an OBD scanner and does not come on at any point during a drive cycle. However, as soon as the car is turned off and back on again, it returns. I have swapped the motor for another one and cleaned the connectors, to no avail. I have continuity from the ECU plug to motor plug.
Any suggestions as to what the underlying cause of this could be? I understand that cars do self-diagnostics during start-up, but why does the ‘check engine’ light appear at start-up and not during normal driving? Paul Vernon
A The code ‘2008’ translates to ‘APV (auxiliary port valve) motor control circuit fault’. This indicates either a malfunction with the motor or a problem with the connection to the motor, possibly an open circuit or a short to ground.
The APV will do a self-check every time the engine is turned off. If you have a faulty or sticking valve, this explains why the ‘check engine’ light illuminates when restarting.
Although you have swapped the motor, you do not mention if you replaced it with a new motor or a secondhand unit. When turning off the engine, you should be able to hear the motor powering back. Another possibility is that if the APV is sticking and was not fully returned when swapping the motor, this may be causing an error. This should normally result in a ‘2004’ code, but would be worth checking. It is also possible that either the gear mechanism or the valve itself is at fault. The only way to confirm this is to strip off the inlet manifold, which is a major task on your engine.
Having checked the continuity between the PCM (ECU) and the motor, and confirmed that there are no short or broken circuits, as long as you have also ensured that the connecting plugs are not corroded, which could impair the connection, the most likely cause is the PCM. In this case, ecutesting.com should be able to test the unit for you, to either confirm or eliminate it as the source of the problem.