QuestionQUESTION: Hi Roland,
I had transmission problems and got those solved with a new output speed sensor and junkyard replacement TCM which resolved the malfunctioning speedometer and limp mode problem. Originally I had a PRND3L switch go bad and the car would not start as well. This was replaced , but has not corrected the starting issue. I can start the car by jumping the starter relay in the power box. I don't have a wiring diagram. With the switch on everything in the car works but I can't engage the starter. Do you think there is a wire problem between the ignition and the starter relay or the stater relay to the PRND3L switch. The PRND3L lights are all lit up when the ignition is on as well as when the car is started. Only R and D light up when you select the gears with the exception of neutral when all the selector lights are lit. I've checked all fuses. I also checked continuity across the stater relay spade and it was fine.
ANSWER: Thanks for the progress report. The authorization to close the starter relay is provided by the p/n switch inside the transmission which when in those positions grounds the brown/yellow wire and the black/light green wire, both side-by-side at one end of the 10-pin plug of the trans. So see if that is happening or not, and then check the black/light green connection at the starter relay socket pin C and to pin 30 of the PCM, and check the brown/yellow at pin 41 of the TCM plug. The ignition switch should apply 12v to the starter relay pin B socket and to pin 8 of the TCM when in the start position by means of yellow wires. So see what isn't happening to find out why the starter doesn't respond.
Roland
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QUESTION: I put a voltmeter on what I assume is relay socket pin C (85 spade on Relay) and got 7v with ignition switch on and 0v with switch off, Sockets corresponding to spades 86 and 87 were 0v with switch on and off and socket corresponding to spade 30 was 11v on and 12v off. I will have to do some dis- assembly and get the car up to do the plug and the wire checks between the PCM and TCM. I assume you were asking me to check continuity only on the black/light green connection at the starter relay socket pin C and to pin 30 of the PCM, and check the brown/yellow at pin 41 of the TCM plug.
ANSWER: Hi Bob,
I don't show the spade numbers you mention, so if you look at the starter relay socket in the power box, the rear pin is called D and the front pin is B.
Pin B (red wire) is connected to the battery and pin D (light green wire goes to starter solenoid switch) receives the 12V from pin B when the relay closes.
Pin C is the inboard pin and that is the one (black/light green wires) that should be grounded by the transmission in P or N (at the pins I described earlier of its multipin socket) and it also is connected to pins 41 of the tcm, 30 of the pcm. That grounding action is what activates the starter relay.
Pin A is the outboard pin and it is the 12v supply from the ignition switch (in the 'start' position) and it provides the power to activate the relay, and it is also connected to pin 8 of the tcm.
Yes, verify all those connections.
Roland
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QUESTION: Hi Roland
Please excuse my ignorance as I am not great with electrical issues. I would like to clarify what I believe you told me. Pin A is coming from the ignition and should be hot when the ignition is turned on to start. Using my voltmeter this is the case showing 12v in the start position. It also shows 12v when the ign. switch is in the off position. I am using the neg probe grounded at the neg battery terminal and the positive probe stuck into the A pin.
Pin C has no voltage with the ign. switch off or on with the neg. probe grounded at the batt. and the pos. probe stick into pin C. If I jump pin A to C the starter engages and the car starts. I assume because I have bypassed the P/N switch in the transmission. When you talk about pin B I don't get any voltage with the ign. switch in the on or off position using the neg. probe at the neg. batt. terminal and the pos. probe stuck into pin B. You said I should I be getting 12v to pin B with the ign. switch on which I am not. Is this in any way controlled by the P/N switch? Do the yellow wires going to pin B and and pin 8 of the TCM come from the P/N switch or from the ign. switch? I am beginning to think it is in the P/N plug or wiring to the plug between it and the starter relay.
Thanks for your patience.
Bob
AnswerHi Bob,
Taking it in order of your questions:
I am not sure why pin A shows 12v when the switch is off. I would not believe that the yellow wire from pin 8 of the tcm would have that on it, again I assume you have the relay removed from the socket. So check that again.
When you say you jump from A to C and the starter starts, that is when the relay is in the socket, correct? If so than I don't understand why because A is already connected to see via a resistor and coil inside the relay, so by-passing that with a jump should not activate the relay. Only grounding pin C will activate the relay.
Pin B should have 12v on it at all time, directly from the battery.
All the p/n switch does is ground pin C, and also it is 'seen' by pin 41 at the TCM and pin 30 at the pcm but that is not the main purpose of the p/n. It is to ground pin C
The yellow wires are on pin A not pin B.
So it appears we have some confusion between us.
Are you sure you have identified the pins correctly? Look at the box lid for ID perhaps.
The first question is, with the relay removed, does pin C show a short to ground (i.e. does it read 0 ohms resistance when the other lead of the probe is connected to the negative post of the battery. If so then the p/n switch is working. It should show a high resistance to ground when the trans is in any other gear setting.
Roland
