Starter relay wiring

15

Asked by Jan 24, 2017 at 11:17 PM about the 2008 Ford F-150 Lariat SuperCrew 4WD

Question type: Maintenance & Repair

My 2008 Ford F150 has been having intermittent starting issues. It has been a rather frustrating process to deal with. I first replaced the battery, then I replaced the starter because I was told it was the problem (tested at Autozone) and finally I replaced the neutral safety switch. I tried switching my starter solenoid relay (R01) with my Hi beam headlamps (R03) relay and there was a half crank but it didn't fix it. When I switched it back I also got a half crank. I pushed and moved the relay around as I turned the key and it started to crank. I let my hand off the key and it continued to crank and started. I tried this again today but wasn't able to get it started at first. Eventually I got the truck started and I think there's not a good contact between the relay and wire going to starter or that wire is bad. I've tried looking into what the wire from the starter ignition point to relay box is called or if it's a specific part but I can't find much. I know from the repair manual that it's yellow/blue wire and I confirmed that looking at the starter but beyond that us unknown. How would I go about testing this wire or replacing it? How can I obtain access behind the fuse panel? Any input is appreciated. Thanks!

4 Answers

I am having the same issue, and cannot figure out what is going on. I also think it is this wire from the solenoid to the relay box. Mine is also a 2008 F150.

15

I isolated the issue on my truck. I tested my started relay (R01) connections. I removed R01 and looked for 12V on pin 30 (constant hot) then I looked for 12V on pin 86 (cranking). These two points of contact have 12V so I knew I was getting power. I then tested the grounds and terminal 87 has a good ground but my terminal 85 does not have a good ground. The PCM (computer) is what allows the signal to ground when certain criteria are met. This is the point where I'm stuck because the only information I could find on this was... the neutral safety switch, crankcase and crankshaft position sensors, or wiring. I've already replaced the neutral safety switch and I don't think it's the crankcase or crankshaft position sensors because the truck runs fine and doesn't throw any codes. Temp Fix- My temporary fix for now is to ground terminal 85 myself. This overrides the computer and allows my truck to start. I wrapped some wire around terminal 85 and grounded it to some metal by my glovebox. This allows the truck to start! Let me know if you need any help walking you through something. Btw I think my problem is the PCM which is expensive so that's why I'm making this temporary fix.

Thanks Jeff. I will check the same thing. Dave in Minnesota.

15

The PCM ended up being bad.

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