I've done the P1689 troubleshooting steps. I made it to the end of step #8. According to the steps, that means my ECM is bad. In keeping with the idea that "it's probably not the ECM," I've been trying to double-check the communication between the ECM and the VP44.
I tried to put an oscilloscope on the VP44 today, to see if I could see the data. If I see the ECM's data, then it's the VP44 computer, not the ECM. I saw something that looked like PCM data, but I couldn't figure out how to set a stable trigger on it.
I put channel #1 on the black & white wires (Pins 1 & 2), and put channel #2 on the green wire (Pin 8). Then I tried to trigger off of channel #2. If I tuned the trigger just right, it would hold-still for a couple seconds. I was expecting that the green wire (sync signal) would provide a perfect trigger.
Does anyone know the correct scope setup to see this signal?
I've done the P1689 troubleshooting steps. I made it to the end of step #8. According to the steps, that means my ECM is bad. In keeping with the idea that "it's probably not the ECM," I've been trying to double-check the communication between the ECM and the VP44.
I tried to put an oscilloscope on the VP44 today, to see if I could see the data. If I see the ECM's data, then it's the VP44 computer, not the ECM. I saw something that looked like PCM data, but I couldn't figure out how to set a stable trigger on it.
I put channel #1 on the black & white wires (Pins 1 & 2), and put channel #2 on the green wire (Pin 8). Then I tried to trigger off of channel #2. If I tuned the trigger just right, it would hold-still for a couple seconds. I was expecting that the green wire (sync signal) would provide a perfect trigger.
Does anyone know the correct scope setup to see this signal?