If you haven’t checked all the fuses yet to make sure power is getting through all of them then do that next. Also make sure all the connections going to the PDC are making sold connection. Maybe you will get lucky there. Move on to the PCM power connections next if you have to and check all the power and ground connections to it using your meter. I doubt that the TCM is bad since the trouble seems to be with the engine systems like the starter, ignition system, and possibly injectors. It would be very worth while to have a factory wiring manual to help you solve this issue. Logical troubleshooting will find the trouble.
The TCM monitors the transmission range sensor input and broadcasts the information on the BUS. If the instrument cluster shows the proper gear position this suggests that the TCM is operational. Without a scan tool it is difficult to determine what the problem might be.
Along with the other checks I mentioned previously I suggest you check for power coming from the Auto-Shut Down Relay inside the PDC. Check for power on a dark green/orange wire possibly on connector C6 of the PDC, pin 5. Fuse 12 supplies power through that relay and to the PCM. Check fuse 13 also going to a red/white wire on pin 9. Both fuses are 20 amp.
I will definitely do the checks you’ve suggested and let you know what I find. My neighbor has a better scan tool than I do so as soon as I can get my hands on it I will try to get some readings. I’ll try to get to the other stuff as soon as possible since it’s supposed to get just a little bit cooler, 100+ degrees is hard to work in.
A scan tool check would be great to do but it won’t help too much with the voltage checks. Though you may get a some sort of circuit error or comm error code if perhaps no power is getting to the PCM.
You have a scan tool and you are not using it? A scan tool will help a lot. Read the transmission inputs into the PCM, be sure it shows the gear position and check the fuel status (on/off/theft).
My scan tool does not have those features it’s a very basic one. When I can get my neighbors his has more features than mine.
I’ve rechecked fuses, power at the ASD and starter relays, rechecked connections, etc, so far they check out. But I’m wondering about the the wire you mentioned to monitor at C1 pin 8 at the PCM. I checked the voltage and it was good with the key off then with the key in the crank position the voltage drops down to anywhere from 125mv to 200mv. That’s a big drop, what should happen?
That is the ground control circuit for the starter relay, the PCM grounds that wire for starting if the transmission is in park or neutral. It seems to be working at the PCM connector but not at the relay, check the connectors under the power distribution center and the harness between the PCM and PDC.
Like Tester and Nevada_545 stated, pin C1-8 controls the Engine Start Relay by making a GROUND connection to the relay coil when the key is in the START position so you should see the voltage go to near zero volts when the circuit is ON. Earlier you stated that you checked that wire and it had good continuity. If all that is true then you should see the same voltage change at the relay on pin 85 and the relay should close. The voltage on the pin should drop to near zero volts, which is ground potential. When you are not in the START position then the PCM circuit OPENS and the voltage goes high due to the high resistance added to the circuit. That voltage comes through the relay coil and then meets the very high resistance of the open circuit inside the PCM control circuit because it is OFF, thus no current flow through the circuit. When the circuit turns ON that internal resistance inside the PCM goes to near zero ohms or ground potential and you now have no voltage potential at that point because all the voltage gets dropped across the relay coil due to the current flow through the relay coil, there is now no added resistance for a voltage drop to take place. If you don’t see that same voltage drop on pin 85 of the relay when in the START mode then that wire connection has a problem.
Adding to the other issues. When doing some checking today I noticed that when you first turn the key to start the MIL/CEL is no longer lighting up as it should but the others, battery, abs, airbag, etc are. I haven’t been able to snag my neighbors better scanner so I used my cheap-o and got a linking error.???
Do you mean there’s no CEL illuminated when you turn the key to “on”, but before turning it to “start” and cranking the engine? Most CEL’s come on when the key is in “on” but the engine isn’t running. That’s done so the driver can verify the light bulb behind the dash is working. How soon the CEL turns off once cranking begins probably varies from car to car.
No check engine light and no response from the PCM with your code reader suggests that the PCM is not powered up or has failed. Test all the power inputs and grounds at the PCM connectors.
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The CEL isn’t coming on at all. When I fist started looking into the no crank no start problem it was coming on that’s why I didn’t really notice when it stopped coming on.
You need to check your fuses and power connections to the PCM like Nevada_545 suggested.
Do you know of a site or do you have access to a pin out diagram for a 97 dodge grand caravan 3.8L? I’ve been using a Chilton(better than nothing) and going by wire color to see which pins to check but a diagram would be easier. One thing kind of different about this van, which makes going by wire color and the manual a little bit of a pain, is the wire colors don’t always match. When the van was purchased in late 97 I had the bigger engine, transmission and a/c put in it and had to wait to get it while that was done. So, what I’m finding is the wire colors for the inside of the van, which had no special orders, match a 97 but in the engine compartment, that was special ordered, match a 98. I know that roughly the 96 - 00 are pretty similar but as I had said before fortunately or unfortunately (for learning purposes) I haven’t had to work on electronics in a car. I know the basics of electronics in any situation but to try to narrow this down better I think a proper pin diagram would go a long way in helping me. I would purchase some online information but unfortunately money is a major problem hence trying to learn and find the problem myself. I really appreciate all the help on this site because without it very little if anything would be getting done. My responses might get kind of sporadic because we’re supposed to have thunderstorms off and on for the next 4 days and no way to cover up the van.
The best money you can spend is for a FACTORY service manual. Here is just one example you can get on Ebay.
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Suggest to start out by checking all the fuses involved in powering the ECM and the OBDII connector.
Four ideas:
- Chiltons/Haynes repair manuals usually contain the most important parts of the wiring diagrams, although they can be confusing b/c they cover several models and model years. At the minimum they’ll tell you which fuses are related to powering the ECM.
- You may be able to find a used factory service manual on ebay or amazon, either in book form or on CD/DVD. The book form is best, if you can find one.
- Check the manufacturer’s website. They may offer a way to view the factory service manual on-line for a small fee.
- The website AllData contains all the wiring diagrams that appear in the factory service manual. It also contains most of the factory service manual explanations of how the systems work, and repair procedures, but in a condensed form geared to a pro auto mechanic. They have a subscription service which allows you to use their repair database for a single make/model/year for a relatively small fee. This is probably your best bet if you plan to continue diy’er repairs for your van.
- Googling might turn up the wiring diagrams too. Or at least the ECM pinouts and wire colors. Owners of cars sometimes post them for others to use. Worth a try at least.
Some good suggestions I’ll look into and see what if anything I can afford or find for free. I’ve checked every fuse in the van several times they are all good. Someone suggested I check the continuity to ground at pin 85 starter relay cavity with a multimeter, what is the correct procedure for this?