'96 Town & Country Won't Start - No Cranking
 

I could use some much-needed help from the experts. Turn the key and nothing. Almost like the neutral safety switch is active.

Last week I changed the valve cover gaskets and spark plugs on our '96 T&C LXI 3.8, 203k miles. That was an ugly job. Afterward the battery was reconnected and it started and ran fine, although I didn't drive it anywhere. I subsequently removed the negative battery terminal again to replace a felt anti-corrosion ring. Went to start it later and no crank. Here's where I am so far:

- Swapped starter relays in the fuse block. No change.
- Jumpered pins 87 and 30. Starter cranks fine. Left key on and jumpered. Won't fire.
- Moved the shifter around. Tried starting in neutral. No change.
- All fuses in both fuse blocks are good (checked with DVM).

When key is turned on, everything comes on as normal. ABS times out and there is no Check Engine light. The only light that's on is the oil light. Turn the key and the ABS light and brake light come on as normal. It just doesn't crank. There's no noticeable voltage drop and the only sound is the relays that engage when the ABS and brake lights come on and time out.

Don't have a manual or electrical diagram yet. Since there's no check engine light I suspect there are no codes. However, I ordered an ODB-II scanner interface. The RossTech equipment for my Audi and VW vehicles isn't compatible.

A manual is something I'll be acquiring pronto as well. Any direction would be greatly appreciated.

Something on the control side of the relay. Does the starter relay click when you turn the key to start? It's a sign the voltage is getting to the starter relay coil from the ignition switch. It also means the PCM is applying the ground to the relay coil. If it doesn't click the relay coil is either missing ignition switch power or the ground from the PCM. Should see 12vdc from the ignition switch at contact 86 of the relay with the key turned to start. Disconnect the battery then check for resistance to ground at contact 85 of the relay.

I'm betting you have the 4 speed 41TH transmission. In that case unless you have an early build 96, you have a Transmission Range Sensor (TRS) as opposed to a park/neutral safety switch. It's installed inside the transmission and tells the PCM the van is in park.

lock and unlock the driver side door with the key see if it will fire up after that.

No, which is why the first thing I did was swap relays. Checking for voltage and grounds and wiring continuity back from the PDB will be the next steps.

Not sure of the transmission type but it was professionally rebuilt 35k ago. I'll have to check on that to determine the lock out switch type. Good information to know.

I thought of that as well - an ignition disable because of a screwed up alarm condition or something. Didn't help. But good thought. I'll be physically checking wiring here shortly.

Good info. I'll check and report back.

Update 4/7/2012
 

First, thank you to those who are taking the time to offer suggestions. I sincerely appreciate it. Keep ‘em coming. Between Easter egg hunts, buying my wife wheels for her car and fixing motorcycles, I finally got a minute to work on the van.

When the key is moved from on to start, both the Accessory and ASD relays activate. They deactivate when the key is released. From what I understand, the ASD relay would remain active if the vehicle were to actually start.

Regarding the starter relay, there is power at pin 86 and no ground at 85, which we already suspected. With the battery terminals removed, the resistance from pin 85 to ground is infinite, or open.

Just for kicks I tried to test the TRS line from the transmission. The mighty Haynes manual shows a wire directly from the TRS to the PCM and lists it as BLK/WHT or BRN/YEL. The BLK/WHT wire is part of the grey lower PCM connector and the BRN/YEL wire goes to the black upper PCM connector. Don't know which one is correct. I removed the connectors and tested both lines while changing gear positions (no power connected). They showed open all the time on both wires. This tells me that even though the schematic shows the device as a physical switch to ground, it’s probably a solid state device that requires power to operate. Regardless, is the signal to the PCM from the TRS supposed to be open for Park and Neutral, or ground? Or is it a more complex signal than that?

I could pull the PCM out where the wiring could be probed under power to see exactly what’s going on if I knew what to look for.

Does anyone make software that can communicate or at least monitor some of the vehicle’s control systems or sensors via the ODB-II connector? I guess that’s probably asking a lot for a 16-year-old domestic minivan.

I decided that if I was going to be serious about fixing this van, I needed high quality, professional reference materials. Picked up a full set of factory service and diagnostic manuals off Ebay for very reasonable. It should help greatly.

the pin 85 is where the ground come is supplied from the pcm so if u turn the key and no ground there then check it also at the pcm see if there is a broken wire or not or ohm out the wire from pcm to relay pin 85.

If only the grounding wire from the PCM to the starter relay was bad then the engine should have fired when I jumpered relay pins 87 and 30 to manually run the starter. Since the engine wouldn't fire, it tells me that the PCM is also inhibiting other functions.

Once I get the factory manuals then hopefully I'll be able to effectively test key inputs and outputs of the PCM to determine if something external is shutting down the PCM, as I suspect, or if the PCM has failed. I'm also going to see if my favorite local u-pull-it wrecking yard has some 96-98 T&C's and Caravans to maybe source a cheap PCM to swap in just for kicks. Could save a lot of time.