Chrysler Repair/1998 T&C stalling and rough idle
Roland, I was not able to respond with a "follow-up" question. That option was not available at the bottom of the page from your last response to me. Is there a limit to the number of times that I can email you from the initial question that was asked? The only thing I thought I could do to communicate with you was to initiate a new question for this problem I am having.
I had the dealer rescan for fault codes this morning. He said the only two codes in the system:
P1698 no CCD message from TCM
P1695 no CCD bus from BCM
The positive temperature coefficients you noted are soldered into the junction block printed circuits. So I did not know how to check the voltage at PTC#1. I checked PTC#1 by noting the voltage of wire #6 (wht/blk) of connector #2 of the power distribution center. It fluctuated between 12.06v and 11.71v with the fuel pump and auto shut down relay constantly clicking on and off.
If you Google "voltage drop test" your first five or so hits that come up can explain it better than I can. From what I have learned recently voltage drop tests are an effective way to test an electrical circuit's ability to deliver power to electrical loads. Voltage drop tests are usually performed to test loads and locate circuit problems. Unwanted resistance in a circuit reduces the amount of electrical energy delivered to the load. Loose connection, corroded connections, broken wire strands, pitted relay contacts, and other physical damage that resists current are causes of unwanted resistance.
I tested the PCM power circuits and ground circuits. I used t-pins to back probe into the connector wires. I connected the positive(+) lead of the digital voltmeter to the PCM power circuit. I connected the negative(-) lead of the voltmeter to the battery positive(+). With key on engine off I measured the voltage drop in the circuit. I did that for the other power circuits I noted to you. Then I tested the ground circuits of the PCM with the voltage drop test. Using t-pins I back probed into the connector wires of the ground pins. I connected the positive(+) lead of the voltmeter to the PCM ground circuit. I connected the negative(-) lead of the voltmeter to the battery negative(-). With the key on engine off I measured the voltage drop in the circuits. The voltage drop should be no more than .05v or 50mv for the power and ground circuits. When there is excessive voltage drop within the power and ground circuit the PCM will have a delayed reaction or circuits controlled by the PCM will not work properly or not at all. Some possible causes for excessive voltage drop are loose connections or corrosion within the circuit.
For the fuel pump voltage drop test I took the fuel pump relay out and jumpered #30 and #87 to have the fuel pump on constantly. I hooked up the meter and leads before turning the key on to activate the fuel pump. Red lead from voltmeter to positive(+) side of battery. Black lead of voltmeter to a jumper wire connected to the power terminal of the fuel pump. I turned the key on to run to see the voltage drop for the power side. Then I hooked up the negative lead of the meter to the negative post of the battery. Then positive (red) lead of the meter to the jumper wire that is connected to the ground terminal at the fuel pump. I turned the key on to let the fuel pump run and checked the meter to see the voltage drop on the ground side. Readings: power side .49v and ground side .17v
Maximum voltage drop should be 0.50v or less.
I recently got this information about voltage drop testing from youtube. I hope they supplied accurate information.
Yes to your question about the fuel pump and the fuel pump relay clicking spontaneously when I turn the key to the run position. Also I should mention that the auto shut down relay is doing the same thing at the same time.
As I mentioned earlier, I replaced the ignition switch because my mechanic though that might be the problem.
The battery voltage was 12.79v after coming back from the dealer this morning. I checked the voltage when I turned the key to 'run' and it was between 12.68v and 12.61volts. The ASD and fuel pump relays were clicking away constantly with the key in the 'run' position.
Correct. the site sets the limit at 2 follow-ups, so a new question is needed.
Based upon your voltage drop measurements, nothing jumps out at me about the items that you focused upon. Thanks for explaining about those techniques.
So then looking at the two fault code numbers, I do have the '98 body diagnostic manual which lists both of those codes and there are a total of 12 pages that give a series of step-by-step tests that should lead you to the conclusion that there is either a wiring issue in the CCD bus circuits or that one or the other of those modules needs to be replaced. I can photo copy those pages and send them to you by postal mail. So tell me your address and I will do that.
I believe that is the most efficient way forward from this point rather than taking it on piece by piece with multiple q and a.
Thanks for the rating and nominations. You can do up to 5 nominations in a month if my answers prove helpful to you.