I have a 2003 Grand Caravan with 84,000 miles that will not crank. The cluster and accessories appear to operate normally when the ignition switch is turned to Run, but the engine will not crank when the ignition is turned to Start. I’ve had the car for 5 years, never a problem. Parked for a few days and then it would not start. Here’s the diagnostic information I have collected so far…
Connected Actron OBDII Scanner, shows no codes stored.
Ignition switch in Run
-Transmission Control Relay engergizes
-Accessory Relay energizes
-Cluster lights up, appears to operate normally
-PRNDL indicators work correctly as shifter is moved
Ignition switch in Start-Run
-Transmission Control Relay remains energized
-Accessory Relay de-energizes
-12V at pin 86 of Starter Motor Relay Socket
-open circuit to ground on pin 85 Starter Motor Relay Socket
Engine cranks by jumping pin 30 to pin 87 of Starter Motor Relay Socket
-does not start with ignition in Run and cranking starter by jumping 30/87
Fuel pump relay does not energize with ignition switch in Run or Start Run
Continuity Checks:
Checked Transmission position sensor at pin 76 of PCM connector. Shows continuity to ground in both Park and Neutral.
Checked continuity of PCM pins 44, 43, and 32 to Crankshaft Position Sensor harness connector-OK
Checked continuity of PCM pins 44, 43, and 33 to Camshaft Position Sensor harness connector-OK

Replaced components:
PCM; same results with replacement PCM and original PCM
Crankshaft Position Sensor; same results as original CPS
Transmission Position Switch
-original TPS failed after disconnecting and reconnecting. Cluster showed all of the PRNDL positions simultaneously illuminated. Replacement operates correctly, only illuminating the PRNDL positions one at a time.

Any help on this problem is appreciated.
Thanks

 

More info...
From what I have read on ALLData, the PCM checks the Park Neutral switch and checks engine speed before grounding pin 85 of the Starter Relay to crank the starter. What is missing from the info I can find on ALLData is exactly where the PCM is getting its engine speed signal. Am I on the right track tracking down the engine speed signal or am I missing something else? Thanks

 

Forgot to mention... 3.3 Flex Fuel, Auto, 2WD

 

More info...
The Vehicle Anti Theft Alarm Light is illuminated solid on the cluster after the 4 sec bulb check is finished. According to the service info on ALLDATA, a solid light "signifies that the Security Key Immobilizing Module has detected a system malfunction and/or that the Security Key Immobilizing System (SKIS) has become inoperative." It goes on to say that diagnosis of the SKIS should be performed using a DRB III scan tool and the appropriate Body Diagnostic Procedures manual. Also worth noting is that an invalid key will set a flashing light, so the problem is not an invalid key.
Any suggestions on where to from here? Thanks

 

It seems like the immobilizer has a problem....only thing to do is get the vehicle diagnosed and pull the immobilizer codes...

 

Had it towed to the shop this morning. I'll post what they find.

 

Result: The B+ circuit feeding ECM pin 46 was corroded in the wire harness bundle between the underhood Power Distribution Center and the PCM. Pin 46 checked OK with a multimeter, but would not carry current under load. Mechanic found it by testing with a light bulb in series with the ammeter function of a multimeter (3 amp load). Ironically I had checked for B+ on pin 46 before I had it towed to the shop. Mechanic did the same at the very outset, but since we were both using multimeters set on voltage the problem went undetected. Next time I'll know better and load test.