A customer recently brought in his 2002 BMW 530i for service and a check engine light.
He said the car drove normally, but was asked to take it in because of the warning lights, which included those that indicated services were needed (brake fluid, oil change, and vehicle inspection).
The customer also noted that he had seen a low battery code on the center display.
Before the test drive, we plugged the car into the Integrated Service Technician (ISTA) application and pulled the diagnostic codes. We pulled Digital Engine 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 that was running low.
Then we tested the car; drove normally.
EVAP examination
Once the car was back in the shop, we started checking the evaporative (EVAP) system. We visually inspected the EVAP lines for damage or wear; We have not found any problems. We then checked the connector on the EVAP purge valve; It was fine.
We then reconnected the ISTA and performed an EVAP purge valve activation test. We discovered the intermittent activation of the purge valve after multiple tests.
The purpose of the EVAP system is to ensure that fuel vapors do not escape into the environment. The purpose of the EVAP purge valve is to ensure that additional fuel vapors from 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 left open, the check engine light will come on and make it difficult to start the car after refueling.
We then replaced the purge valve and ran the EVAP test. The bleed valve worked fine every time.
After that, we tested the battery charge; it was at 10.2 volts at 300 amps. Normally, this would be fine; however, when we checked the date stamp on the battery, it was from June 2013. Since the car was putting a dead battery code and the battery was 10 years old, we replaced it.
After the service and diagnostic work, we tested the car and ran monitors. All monitors worked except EVAP which can sometimes take up to three days to do so.
EVAP needs ideal conditions to pass the monitors. Because of this, EVAP is the only monitor that does not have to pass an emissions test.
We then left the car with the customer and told him to come back in a few days to check the monitors.
Diagnosis of the problem
Two weeks and 480 miles later, the customer called back to tell us that the check engine light was back on.
Once the car was in the shop, we pulled codes and found that P0444 (EVAP System Purge System Insufficient Flow) was stored in memory. We have done all the tests on the bleed valve but have not found any problems.
At first, we thought we might have gotten a bad bleed valve, but that would be extremely rare.
We then took the diagnosis to the next level and performed a check of the main wiring termination in the DME (main power train computer). When the DME connector was off, we could see engine oil on the computer pins.
Then we found engine oil in the DME connector. We were subsequently able to trace the engine oil through the wiring to the exhaust camshaft sensor.
An unusual discovery
The exhaust cam sensor had cracked and was leaking oil into the main engine wiring. This was extremely unusual as the exhaust cam sensor had not failed electrically and was not setting any codes.
Either way, the exhaust cam sensor had to be replaced and the wire harness and DME cleaned. After replacing the exhaust cam sensor and cleaning the wiring and computer, all was well.
This diagnosis and repair was quite interesting, because it is very rare for oil migration to occur in this engine. The oil only migrated to the DME and not the bleed valve.
In the end the bleed valve had failed on its own and oil migration caused the second code. Looking at the two bleed codes and the broken bleed valve, one would think that the valve caused both codes.
Even when you think you’ve seen it all, you might be surprised.
