Is the answer right under my nose?
Used car lot. Dead battery on arrival. Complaint is stalling, barely made it off the trailer on its own power. P0660 is the only fault i see at first. I try to crank multiple times with no start.Finally starts but stalls as soon as i touch accelerator. Check faults again and P0340 and P0339 show up. So I scope the signals. I used a long time base but could see sensors not pulling all the way up. So I called the sensors. Install, vehicle starts. I do cam/crank relearn, vehicle revs all is good. Nope, stalls out again. I check codes and same three are back. Odd so I scope again with shorter time base. I notice odd events happening. Green trace is crank, yellow is cam.
These next three waveforms are all the same crank cycle and during cranking.Control is green and 5v is yellow for manifold tuning valve. Clean on off signal 3-5 volts. I know thats odd but also there is a glitch in the next capture then the final capture shows lots of hash. Very weird as well. I load test ground and is good.
Ill be going back to this vehicle later this week but I didnt get anywhere with it. Also, once it was time to go I decided to scan faults again and the rest of these codes popped up. If anyone has anything to add it would be appreciated
Disconnect BK 2 O2 sensor. See what happens.
Would a wiring diagram help , see what those sensors have in common ? That could be affecting them all. Also could test the alternator. Regards Dave T...
It looks like the reference voltage is your problem. I can't tell you what is causing it do drop. Gail may be on to something with the O2. I would focus on having stable 5v ref before anything else.
Gail and Blake, I called the lot and asked them to unplug the 02 and same symptoms. I see the 5v signal is an issue. Im building a strategy for when I return to the lot and will update . Stay tuned
Chad, Many of these vehicles have a single ground on the transmission. You may want to clean the ground surfaces and see if that helps. I had a similar vehicle that was a no start and the ground was to blame.
I would scope reference and grounds to sensors...also scope power and grounds at the pcm and dlc...faulty coil? alternator?
I have scoped the reference and the 5v feed is good. I don’t know if a safe way to load them but with the scope shows good. I load tested “some” grounds and they passed. The alternator did raise some suspicion to me at first as it had lot of ripple but I attributed that to the battery being dead On arrival. I may unplug the alternator
For those interested I was unable to find the issue. I connected my scope as such, channel one was 5v and ground on return wire. Channel two was signal wire. As the signal dropped on channel two channel one 5v was perfect. These drop outs were random so I knew it was not mechanical. 5v was good so I thought, either faulty new sensors or pcm. Since the wave form was just as bad with new autozone…