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my oil cooler fan has been cycling low high speed constantly, i diagnosed a faulty ballast resistor and have now replaced both the ballast resistor and the oil temp sensor "while i was in there".
The fan still pulses, I suspect because the ccu still has fault codes recorded. My car is a fairly early one and has an custom DME ROM both of which may limit the ability to connect with aftermarket odb tools from what I read of others experiences.
I have tried a pdt999 but was not able to connect to any of the cars components.
Is there a jumper on the odb port or on the ccu itself to reset the fault codes without an odb tool or will it clear automatically after a certain number of power cycles?
I have tried a pdt999 but was not able to connect to any of the cars components.
Check the L-line/diagnostics fuse, i think its #1 or #20 or ???
Originally Posted by alexjc4
Is there a jumper on the odb port or on the ccu itself to reset the fault codes without an odb tool or will it clear automatically after a certain number of power cycles?
The only control unit with non-volatile memory is the airbag controller. So just pulling the ground connector on the battery for 1 second is enough to erase all the fault codes and the DME ECU idle speed adaption value.
Cleared or stored fault codes in the CCU does not affect the operation. Once you get the oil cooler fan problem fixed, it will work as designed. There's no other way to clear the codes other by using a compatible OBD diag tool.
I would start with checking the oil temp sensor readings with an ohmmeter connected to the CCU harness connectors. Normal sensor value at 20 degrees C is 22.6kOhm. Measure on pins G12 and G18.
I suspect your oil cooler fan feedback circuit to be faulty, either a wiring fault, or an internal CCU fault. Use an ohmmeter to check connection between CCU harness pin G9 and one of the terminals on the fan motor.
How do you connect to the diagnostic port? Are you using a OBD2--to-19-pin adapter bought off eBay or similar? These are sadly always wrongly wired.
Thanks Tore, I measured the oil sensor directly and old and new were in spec. The ballast resistor showed some corrosion and was 1.5ohm rather than 0.5ohm, i dont know if that's enough to trigger a fault. I'll measure both at the ccu.
The odb connector was the one that comes with the pdt999 and works correctly on another car.
Turns out the CCU sensor fan was unplugged (probably since I've owned the car - its always done swinging temperature thing on long journeys so i had suspected something like this), plugged it back in and it ran with a little grumble, pulled it all out blew it out with an air line and greased the bearings, while i was in there reflowed a couple of dubious solder joints. I quickly verified the ccu fan was switching off (eventually) after ignition switch off, as I was concerned it may have been unplugged due to battery drain rather than due to noisy bearings.
Checked the oil temp sensor resistance at the ccu harness and it is in spec.
Couldnt figure out a quick way to check connectivity between the ccu and the oil cooler motor so I tried swapping out the relay r04 for the one I removed when I deleted the engine blower.
Bingo, oil cooler no longer pulses, looks like it was simply a failed relay all along, wow that was a long way round to get to that answer, lol my world class diagnostic skills strike again!
Tested the relay, a rivet failed on one of the pins causing intermitent fault on one of the two solenoids. Looking at the way it failed it could easily have happened while removing and inserting the relay while I was diagnosing the original issue.
04-18-2015, 04:13 PM
clearing ccu fault codes without obd?
