1997 dodge grand caravan LE 3.8L The van started okay, let it warm up for a couple of minutes. Then put it in reverse backed up a few feet then it died. When I went to restart it I had a no crank no start problem. Checked the battery it was okay, but tried a jump start anyway but nothing. Checked the fuses and relays even swapped out the relay just in case still nothing. Checked that the starter is getting power and it is gave it a few taps and still nothing. If you put a jumper wire across pins 30 and 87 the starter will work but engine will not start and that is with the key held in the full start position. If the key is in full start position with the lights on the lights do not dim at all. While it was running the only thing done was the MAP sensor was replaced and the van was started and run numerous times since then. Because I didn’t have any signal to pin 85 at the starter relaying in the pcm someone suggested the neutral safety switch (on mine it’s a transaxle range sensor which is in the transmission not on it, just mu luck), replaced it but didn’t help. Checked for signal at the pcm from the ignition switch and it had a signal so most likely not that. Wires and harnesses have been checked and so far nothing has been found but with the age of the van it could still be a possibility. I know some basics about cars but if suggestions of things to try could be put in very basic and detailed directions I would really appreciate it. Thanks
Figure out why it doesn’t crank as the first step. Do you have at least 10.5 volts on both starter motor terminals (measuring terminal to starter case) during attempted cranking, when the key is in “start”? If you do and it doesn’t crank, then replace the starter motor.
I checked the starter before but was hot and tired I might as well give it another go just to be sure. I’m fairly good with cars but most of my work has been mechanical never really had to deal with electrical. So, just to be 100% I did everything right would you mind going over step by step on checking voltage to make sure. I do have a DVOM. When jumping from pin 30 to 87 at the starter relay the starter cranks does that show or prove anything?
What I do is attach some long test leads to the starter motor so I can crank the engine with the key from the passenger compartment while I look at the meter. It’s a little easier doing this with an analog meter (the kind with the needle that sweeps), but it can be done with a digital meter too. If you measure at least 10.5 volts in both cases, and it doesn’t crank, the starter motor is probably faulty.
These are the two voltage measurements you need to make.
case 1: B terminal on starter to starter case (B terminal is the one with the thick wire)
case 2: S terminal to starter case (S terminal is the one with the thin wire )
I’ll definitely give the starter another check just to be sure. Same as the old saying measure twice cut once. Ha! I’m going to try to get to it tomorrow.
Re-read original post, You need to find out why pin 85 isn’t getting power when key is in crank/start position.
You’ve already done safety neutral switch, How about the ignition switch ?
[quote=“RB533, post:3, topic:121466”]
When jumping from pin 30 to 87 at the starter relay the starter cranks does that show or prove anything?
[/quote] That there’s probably nothing wrong with starter.
My transmission has a transaxle range sensor (inside transmission instead of on it, just my luck) which basically does the same as the neutral safety switch and that was replaced. Have given the wires a pretty good going over but that doesn’t mean I didn’t miss something. At pin 85 I have nothing but when I run a jumper from ground to pin 85 the car cranks. My understanding is if I have power(with a test light) to pin 86 key in the start position then the ignition switch is working.
If I recall correctly pin 85 is a ground controlled by the PCM, the transmission range sensor input is necessary for the PCM to chose to ground that circuit.
Is the transmission position display in the instrument cluster working correctly? If the check engine light does not light when the ignition is switched on that suggests that the PCM is not powered up or is dead.
In another tread you mentioned a lot of monkey business with switching PCMs, if the wrong PCM was installed the vehicle theft security system may have been switched on. A scan tool can show you if the no start condition is due to VTSS.
Sorry! Dang it, I meant to go back on the other thread and fix my mistake. It was not the PCM that was replaced it was the PDC Power Distribution Center) where the under hood fuses and relays go. Before the range sensor was replaced the transmission position display was acting up but with the new sensor it’s back to normal. The check engine light does come on when the key is turned on and all the other indicator lights come on and then go off correctly according to key positions. From what I can gather so far with the new sensor, the indicator/warning lights coming on and the readings I’m getting at the other starter relay pins(not 85), and having continuity in the wires from the sensor and the tcm to the pcm the sensor and ignition switch should be OK and it seems the wires are good. Sound about right? Where from here.
So you have tried each gear position; reverse, neutral, drive, second and low and the display is accurate.
Check for 12 volts for pin 86 when the ignition is in the crank position.
Double check the connectors in the bottom of the PDC to see if one is loose. Pin 85 is controlled by the PCM, the wire color is orange/tan. Monitor the voltage of this wire at the PCM connector C1, cavity 8.
Each gear position indicates correctly. I have 12+ volts at relay pin 86 and 12+ volts at pin 8 at the pcm. I also checked continuity between pcm pin 8 and relay pin 85 and it was good. When using a DVOM I have 12+ volts at pin 85 but when using a power probe or a test light I get nothing.???
high impedance voltmeters can read a voltage that is behind a high resistance. Once you put a real load on it, such as the test light, the voltage goes to zero. In this case the test light is the better choice.
Unfortunately I had a feeling you were going to say that. If it’s been gone over before I appologize, what if anything can I do to try to rule in or out the pcm and tcm as the culprits?
I know that the signal goes in a certain direction and tells things what to do and when. Since I don’t have signal at starter relay pin 85 I need to find out what’s causing it. To try and find out if it’s the tcm or pcm, since the range sensor has been replaced, does the range sensor send signal to the tcm and then it tells the pcm to ground. If that’s the case what wire do I check from the sensor to the tcm? If I have continuity through the wire at that point how do I check to see if the tcm itself is receiving that signal? Then if the tcm is receiving that signal which wire would I check to see if there’s continuity from the tcm to the pcm? If I have that backwards and the pcm doesn’t get it’s signal to ground from the tcm then what direction should I go?
There are communication lines between the TCM and PCM, you will need a diagnostic scan tool to read the data. Have you checked for fault codes? Check all the fuses and inspect for damaged wiring.
According to the diagram posted by Tester above, you should have battery voltage and a test light should light when probing pin
85 86 whenever the key is in the “start” position. That however is not sufficient to cause the crank to occur. For the crank to occur you almost must also have 0 volts (ground) on pin 85. That ground comes from the ECM (i.e. PCM), which presumably will only provide it if it thinks it is safe to crank the engine; i.e. the transmission is either in P or N. When you have battery voltage on 86, and ground on pin 85, the “engine starter motor relay” will be energized, and send battery voltage (via fuse 5) to the thin brown wire attached to the starter motor (labeled E19, usually referred to as the starter motor “S” terminal). The other wire attached to the starter motor (red, thick wire, labeled C1, but usually referred to as the “B” terminal) is always connected directly to the battery, so it should always have battery voltage on it. The yellow/red wire you see on pin c8 of the PSC at the top appear to be an output, signaling the transmission module the key is in “start”.
Like I mentioned above, the first test I do for this problem , before doing anything else, is measure the voltage at E19 and C1 of the starter motor (between the pin and to the starter case) when the key is in “start”.
A correction needs to be made to the first sentence of the previous post. When the KEY is in the START position and things are working correctly in that circuit you should have very little or no voltage on pin 85 of the relay. That is the return or ground side of the relay coil. Pin 86 should have voltage on it whenever the KEY is in the START position. I think G-S-J1 just made a typo because the other info about the circuit operation is correct.
By manually grounding pin 85 you proved that the starter relay circuit works and the problem is with the control circuit for that relay, the engine starter motor rly ctrl , which appears to be inside the PCM. Make sure all the fuses in the PDC panel are good. If that is okay then I suggest you make sure all power connections to the PCM are good. If you have no problem with that then you might have a faulty PCM. Since the ignition doesn’t seem to be working and possibly the injectors also, it seems there may be a power problem to the PCM, in my opinion at least.
Unfortunately I have a feeling it’s the pcm. I also thought that going over the wires and connections to and at the pcm is probably the last things I can try before replacing the PCM. With the testing I’ve done so far what do you think the odds are it could be the tcm causing the problem? Reason I ask is in other posts I’ve read generally people with pcm problems have more than one problem. As I said that’s generally the case but I know it can have just one. Since money is extremely tight I’m just trying to be as sure as I can, without having some serious diagnostic equipment, that I’m going to be replacing the problem.