First real post other than my "hello". I recently bought a 2003 986 2.7 Boxster from an auction to work on with my son as a project. I've got one electrical issue that I'm somewhat stumped on. I've searched the forum and the internet and the answers tend to be localized to a specific sensor, which I don't think is the case here.
My issue a series of codes and other symptoms that I think are all related. Stepping on the accelerator does nothing. The car starts up and runs but it idles rough and its revs fluctuate. Probably runs a bit rich too. I've run a scanner and it throws all these codes with those that say "tap to search" are Porsche specific and I went and looked them up and inserted the issue after the parenthetical.
P0103 (Confirmed) - Mass or Volume Air Flow "A" Circuit High
P0132 (Pending) - O2 Sensor Circuit High Voltage Bank 1 Sensor 1
P0138 (Confirmed) - O2 Sensor Circuit High Voltage Bank 1 Sensor 2
P0152 (Pending) - O2 Sensor Circuit High Voltage Bank 2 Sensor 1
P0158 (Confirmed) - O2 Sensor Circuit High Voltage Bank 2 Sensor 2
P0223 (Confirmed) - Throttle/Pedal Position Sensor/Switch "B" Circuit High
P1120 (Confirmed) - Manufacturer-specific code (tap to search) Throttle position sensor malfunction
P1138 (Confirmed) - Manufacturer-specific code (tap to search) Throttle position sensor 1
P1140 (Confirmed) - Manufacturer-specific code (tap to search) Throttle position sensor 2
P2135 (Confirmed) - Throttle/Pedal Position Sensor/Switch "A"/"B" Voltage Correlation
Given the majority of these codes indicate a high voltage issue, I'm thinking this is more of a centralized issue than a specific sensor being bad. Of course all of the codes are related to the air intake / exhaust system. I also found a receipt in the car from last month for installation of new O2 sensors and can confirm there are new ones under the car. There are no part numbers on the receipt and can't tell numbers just by looking at them. I assume the prior owner didn't spend $780 on new o2 sensors and not be able to drive away from the repair shop. Electrical stuff is a weak spot of mine.
I did take the throttle body off and it was reasonably clean. Cleaned it further and reinstalled. Also replaced the engine air filter - the old one was disgusting and the foam top disintegrating. One symptom we noticed after replacing the throttle body was that after starting, pressing the brake pedal caused the engine to increase RPM a bit and then stall the engine. The other thing I'm noticing is that when turning the ignition key off, right before off the engine revs a bit and sounds better for the split second prior to shutting off.
I did start the car without the MAF plugged in. Engine idles smoother when unplugged but still no throttle response and still has Throttle and o2 sensor codes.
I've also swapped relays in relay panel 2 (trunk) for position 2 which includes the O2 sensor heaters and doing so didn't do anything.
I'm really a novice at the electrical stuff but I'm learning. I purchased the Bentley manual and have the circuit diagrams. One of my theories is that there is a short to power somewhere causing the high voltage readings at these sensors. Another is that the relay / switch at the ignition key is bad causing the high voltage. I'll probably have a new theory later today. My assumption is the accident that damaged the control arms and did some other undercarriage damage may have cause the electrical issue. Between the need for new control arms and the mysterious electrical condition the prior owner donated the car to charity and that is how it arrived at auction.
If someone could help us diagnose the issue that would be great. I have a multimeter and am purchasing a back probe kit.
Thanks in advance
Linear Mode
