Last month, we had a new customer bring in his 2019 Subaru Outback 3.6 liter. He stated that the check engine light was turning on intermittently. We asked him if there were any other symptoms. Besides the check engine light, he could not smell, feel or see any other symptoms. We made an appointment and the customer brought the car in.
Upon the car’s arrival, we noticed the check engine light was not on. We then connected it to the Subaru Select III factory scanner and ran a system-wide scan. There were no codes in the Engine Control Module (ECM), but there were several low voltage codes and communication codes in the antilock brake module, the body control module and the climate control module. We found this a little curious as none of those modules will turn on the check engine light. We then checked the engine control module again to see if there was any stored data. There was none.
Low voltage and communication codes are interesting because there can be many different things that cause them. They can be caused by loose or corroded connections, rodent damage, component failure, ground and power issues, etc. When opening the hood, we found the fuse box cover not on the fuse box. We then checked to see if any of the fuses were missing. All fuses were in place. We then installed the fuse box lid. The next thing we did was test the battery. The battery tested at 9.9 volts at 300 amps for 15 seconds. The battery passed the load test. We then checked for a parasitic draw. After the car fell asleep, the draw was 38 mA. The draw was acceptable. We then performed a conductance test on the battery, and it failed. A conductance test checks the battery’s ability to transmit current and the battery’s overall health.
Since we were getting low voltage codes and the conductance test failed, we called the customer and got the OK to replace the battery. We also suggested cleaning the throttle body as the car has 78,800 miles. Subaru throttle bodies tend to get coated with carbon, and after we change the battery and clear the codes, the throttle body will lose its adaptation. It is not good to adapt a dirty throttle body.
Before the battery replacement, we cleared the car codes. We then replaced the battery, cleaned the throttle body and then ran the throttle body adaptation. We then test-drove the car to set monitors. On the second test drive, the check engine light came on. We brought the car back to the shop and pulled the codes. We pulled an engine control module (ECM) code P000C and a slow response camshaft. The camshaft’s actual position differs from what the powertrain control module expects.
This engine has four camshaft gears that can phase (change the cam gears’ position). If the engine does not have enough oil or if there is a lot of carbon in the oil, the cam solenoids get starved or clogged, and the gears will not work properly. Before all of this, we checked the engine oil level, and it was OK. We then checked all the connectors to each cam solenoid. The connectors were OK. Each solenoid has a position. P000A is the right-side intake, P000B is the right-side exhaust, P000C is the left-side intake and P000D is the left-side exhaust. We then checked for a blockage on the left side (P000C) solenoid but could not find one. We then pulled the P000C solenoid to check its operation. It was switching outside the car, but that does not mean it would work properly in the car. We then suggested that we perform a Subaru engine oil flush, then an oil change and replace the P000C cam control solenoid.
Once the work was performed, we cleared the codes and readapted the throttle in more time. We then test-drove over 80 miles to set monitors and to confirm the repair. After our test drives, all the monitors were completed, and no codes. I then waited about two weeks before calling the customer to confirm the repair. The customer told me everything was good and there was no check engine light.
This was an interesting repair because the P000C code was not in the car when we received it. The car’s internal network could not process the issue due to the battery’s health. Once the battery was replaced, the engine control module could run the appropriate tests. During those tests, the ECM saw a discrepancy between the cam gear positions. In the end, this car had a bad battery and left-side upper cam solenoid. This repair shows how important a stable power supply is to the car’s network.
Matt Pataky owns Sunnyvale Foreign Car Service, 15 Pioneer Way, Mountain View. For more information, call (650) 960- 6988, email [email protected] or visit sunnyvaleforeigncar.com.
