When I start my car using jumper wire between starter relay pins 30 and 87, is that actually bypassing the PCM? Does that mean the PCM has burnt connection on mother board at the starter relay connection? If so why is there good continuity between starter relay pin 85 and PCM pin 31?
I’m also wondering if I drive my car using the jumper method to start car will it damage anything else on my car to keep starting my car using that method until I figure out if it is PCM or some other module.
Here is what I’ve done to diagnose so far, my 2003 Dodge Grand Caravan 3.3L V6 won't crank using ignition key. After verifying the battery and wires to starter are good, I disconnected the battery positive and negative to check continuity of starter to relay. I got the wiring schematics and checked continuity. The continuity from the starter relay pin 85 to pin 31 on PCM is good. The continuity from starter relay pin 87 to starter solenoid plug with yellow and gray wire is good. I replaced the battery negative and positive cables back attached to battery then turned on key and when I turn ignition to start position then it just clicks at relay starter so I know power is coming from ignition switch when turned on and the starter relay switch clicks. Then I turned on the ignition key to ON position, then I used a wire between pins 30 and 87 of starter relay to crank the starter and the motor cranked and engine ran. I can drive the car around and it runs fine until I turn off then it won't start with key but will start when I use jumper between starter relay pins 30 and 87. So I thought the relay may be bad between the other contacts but no, the relay is good. I swapped it around in other spots such as heater blower and it works the heater blower so I know relay is good. I performed a diagnostic on ignition switch that I read about which is to turn key to ACC and try the power mirrors and the wipers, then turn key to on position and again operate the power mirrors and wipers, they worked fine in both ACC and ON position so don’t think it’s the ignition switch.
So I am thinking it is my PCM but I want to be sure before replacing it.
I did the key dance and got OBD code P1684 which has several possible causes according to the OBD data base at Auto Codes, autocodes.com/p1684_dodge.html shows that code P1684 indicates battery disconnected with last 50 tries, it also lists faulty Transmission Control Module (TCM,) the TCM wiring harness, and the other wires of the TCM. I guess now I have to figure out how to test TCM stuff.

 

If the starter bounces when you're cranking BUT you can jump the controlled side and the starter moves normal, then that means the PCM does not have sufficient ground to pull in the starter relay, OR the ignition feed side is low voltage or high resistance. Most of the time I've seen this on that generation minivan, there is battery acid inside the main wiring harness eating away.


You're bypassing the PCM and any PCM starter inhibits related to security possibly trans shifter position, yes.

 

Thank You!

 

TNtech, when you mentioned battery acid it made me remember that a while back before I replace this battery the old one used to get bad corrosion build up on negative post. I cleaned with water and baking soda, it ran all over the PCM and the wiring plugs on the side of PCM. When I did the continuity test on the PCM plug pin 31 to starter relay pin 85 I noticed inside the plug looked sort of like corrosion around pin openings, it is white crusty looking stuff. Should I disconnect battery and then use wire brush to clean the inside of the plugs?

 

I wouldn't brush the pins, but if you can find a substance called "Rusty", (orange and white can) it works really well at breaking up and neutralizing battery acid. Electric contact cleaner is good for oxidation, but not acid corrosion. Put some dielectric grease in the connectors when you're done cleaning.



I have had a few minivans with minor acid intrusion into the harness bundle and a good soaking of this does a good job of slowing it down. Be sure to slice an opening at the lowest point of the harness where it makes a loop down under the car so any moisture can drain from there.




You also need to check your body grounds in the engine compartment. I believe there is one very important one UNDER the battery tray.

 

Thank you!

 

My pleasure. Come back and see us

 

TNtech, I couldn't find "rusty" as you suggested but the LYNX on left in picture is supposed to neutralize battery acid and be able to spray into the wiring harness according to the auto parts store manager. The QD Cleaner is for oxidation cleaning and then the dielectric grease for after contacts are cleaned. I will work on going through all the wiring harness and grounds as you suggested. I'll post results when done.

 

Hey you're ready !!

 

The weather decided to rain on my parade so I can't work on car in the rain and supposed to rain all weekend so I'm gonna clear space in garage so that I can get car inside garage. I was wondering something and thought I'd ask you to help me understand how the electrical flows in the starting system. As I mentioned in my original statement, I did a continuity test on the PCM pin 31 on harness to the starter relay slot pin 85, and there was continuity there so if I understand the way the starting system works when the key is turned to start it sends a signal to the PCM and then the PCM sends a signal through pin 31 to the pin 85 on starter relay and that causes the relay to activate so that pin 30 and 87 flow to solenoid and the starter engages and cranks the engine. Is that correct? If there is continuity from PCM 31 to starter relay pin 85 then that should mean the message would be able to come from PCM to starter relay, or am I not understanding the continuity test result?