My 2008 Ford F150 has a no crank no start issue. The starter relay has constant hot on terminal 30 and hot when cranking on terminal 85. My problem is with the ground side. I have a good ground on terminal 87 but terminal 86 that comes from the PCM is not grounding. I'm assuming it has something to do with the computer (PCM) but I'm not sure. I already replaced the neutral safety switch and I don't think it's the CKP or CMP sensors because the truck runs fine otherwise.

 

The PCM enables the starter relay only after PATS approves the key. What is your THEFT light doing when you make an attempt.

 

The light has the typical 2 second blinking and then when I turn the key to run it times out for 3 seconds and doesn't come back on unless I turn the key back to ACC or off. From what I've read I think that is the normal functioning of it but I'm not 100% sure.

 

Yeah, that is normal. At least PATS can be eliminated as the cause.

You're not supposed to, you supposed to be measuring the small resistance of the coil of the Bendix and the starter motor windings.

It's not supposed to, pin 86 is supposed to be HOT IN START via the ignition switch and the DTR switch.

Pin 85 is supposed to be grounded when the PCM gives its approval. With pin 86 HOT and pin 85 grounded, the relay is supposed to energize activating the starter motor. Pin 85, if not grounded, would measure HOT if the switches are in order.

 

ok can you explain that again. The last stateen wasn't clear to me. Pin 85 should be Hot when on start position or ground ? I'm having same issue and was thinking the ground is my issue.

 

If the PCM doesn't ground pin 85 (PATS approval), then pin 85 will read battery voltage in START and the relay won't engage and the engine won't start.

Both logical conditions must be TRUE (key in START and PATS okay) as well as all wiring and switches involved must be okay to start.

 

I'm working on a 2007 f250 no pats system .I tried to post a wiring diagram .guess i didn't load it right.I know half of the relay circuit is right.I can jump the relay 30 to 87.truck starts.so my problem seems to be in the 85 side.don't mean the hijack post but my problem seems to be same issue.

 

You should have said that up front, then I wouldn't have wasted my time explaining something that doesn't apply.

 

Gas, diesel, automatic or manual tranny?