BMW’s oil migration makes for tricky repair

The customer also noted that he had seen a battery-exhausted code in his center display.

Before the test-drive, we connected the car to the Integrated Service Technical Application (ISTA) and pulled the diagnostic codes. We pulled digital motor electronics (DME) codes P0443 (evaporative system purge control valve circuit malfunction) and P0444 (evaporative system purge system insufficient flow). There was also a code for the battery being exhausted.

We then test-drove the car; it drove normally.

Examining EVAP

Once the car was back in the shop, we started to check the evaporative (EVAP) system. We visually inspected the EVAP lines for damage or wear; we didn’t find any problems. We then checked the connector to the EVAP purge valve; it was OK.

Next, we reconnected the ISTA and performed an activation test of the EVAP purge valve. We discovered intermittent activation of the purge valve after multiple tests.

The purpose of the EVAP system is to make sure fuel vapors do not escape into the environment. The purpose of the EVAP purge valve is to make sure the extra fuel vapors in the EVAP system can be burned off in the engine when it is at operating temperature. If the EVAP purge valve stops working or is stuck open, it will turn on the check-engine light and make it difficult to start the car after refueling.

We then replaced the purge valve and ran the EVAP test. The purge valve worked just fine every time.

After that, we load-tested the battery; it was at 10.2 volts at 300 amps. Normally, this would be OK; however, when we checked the battery’s date stamp, it was from June 2013. Because the car was setting a battery-exhausted code and the battery was 10 years old, we replaced it.

After the service and diagnostic work, we test-drove the car and ran monitors. All of the monitors ran except for EVAP, which can sometimes take up to three days to do so.

EVAP needs ideal conditions to pass the monitors. Because of that, EVAP is the only monitor that does not have to pass an emissions test.

We then released the car to the customer and told him to bring it back in a few days to check monitors.

Diagnosing the problem

Two weeks and 480 miles later, the customer called back to tell us the check-engine light was on again.

Once the car was in the shop, we pulled codes and found that the P0444 (EVAP system purge system insufficient flow) was stored in the memory. We ran all the tests on the purge valve but could not find a problem.

At first, we thought we may have gotten a bad purge valve, but that would be extremely rare.

We then took the diagnostic to the next level and performed a pin out check on the main wire harness to the DME (main powertrain computer). When the DME connector was off, we could see engine oil on the computer pins.

We then found engine oil in the DME connector. We were subsequently able to trace the engine oil through the wire harness back to the exhaust camshaft sensor.

An unusual discovery

The exhaust cam sensor had cracked and was leaking oil into the main engine wire harness. This was extremely unusual, as the exhaust cam sensor had not failed electrically and was not setting a code.

Either way, the exhaust cam sensor had to be replaced and the wire harness and DME had to be cleaned. Once the exhaust cam sensor was replaced and the wire harness and computer cleaned, everything was good.

This diagnostic and repair were quite interesting, because it is super rare to have oil migration on that engine. The oil only migrated to the DME and not to the purge valve.

In the end, the purge valve had failed on its own and the oil migration caused the second code. By looking at the two purge codes and the purge valve being broken, one would think that the valve caused both codes.

Even when you think you’ve seen it all, you can be surprised.

Matt Pataky owns Sunnyvale Foreign Car Service, 15 Pioneer Way, Mountain View. For more information, call (650) 960-6988, email sfcsmv@gmail.com or visit sunnyvaleforeigncar.com.