96 855t, No Start, No Spark

[jalwlb]

This has been the strangest turn of events I've experienced with this car: Early last summer while idling in park one time the engine started randomly revving--but only this one time. This fall after sitting parked for a month, the engine cranked but would not start for the first time ever (132,000 miles). The yellow up arrow flashed and fault code P0120 showed. I changed the throttle position sensor. It looked to be original. The green o ring was dried out and the internals showed corrosion. Still no start, still getting the flashing yellow up arrow and code P0120. I have no spark. Within the past year I have changed the plugs, wires, cap and rotor (all OEM), and the coil (had a multiple random misfire code last winter before changing it). I changed the cam and crank position sensors. Same symptoms.

Today I've discovered a broken wire (the 20 gauge black striped, orange wire) under the plug for the gray fuel system relay above the radiator. It looks as though the insulation cracked right where it goes into the plug for the relay and moisture has corroded the wire to the point of breaking. The copper end is green.

I'm hoping someone with more experience than I might suggest the best way to reattach the broken wire to the fitting the relay pin slips into. Should I replace the whole wire? Where is the other end of this wire? It looks to me like I'll have to cut into the plastic assembly the four wires go into to remove the fitting for this wire. Is the fitting crimped on and buried in silicone caulk?

Thanks for any advice! And who wants to bet this broken wire is the cause of my no spark? Not me at this point.

[misha]

That grey relay on a fan carrier is a Master Fuel Injection Relay.

If there is a disconnected wire from it,it should be a good reason why the engine will not start.

[jalwlb]

misha wins the prize! Once the wire was reconnected the engine fired right up and is running perfectly.

I used a dremel tool on the plastic block of the wiring harness so I could pull the female snap terminal and its hood out, I pulled the terminal out of the hood, stripped the red plastic off a new snap terminal, squeezed the cylinder to match the diameter of the old terminal, crimped on a 20 ga. pig tail, pulled the wire through the original hood and pressed in the new terminal using a little silicone, fished the wire through the block and pressed in the newly hooded terminal using a little more silicone, butt end connected my pig tail to the orange wire on the car with more silicone...

So anyone with an 850 that won't start, a flashing yellow arrow and a P0120 code, check the skinny, black striped, orange wire right where it enters the plastic block of the wiring harness for the gray fuel system relay above the radiator. The insulation on that particular wire is brittle on my car.

[misha]

misha wins the prize! Once the wire was reconnected the engine fired right up and is running perfectly.

It was so obvious.

...So anyone with an 850 that won't start, a flashing yellow arrow and a P0120 code, check the skinny, black striped, orange wire right where it enters the plastic block of the wiring harness for the gray fuel system relay above the radiator....

A flashing yellow arrow is indicating transmission error.
In your case...P0120 code means accelerator pedal (AP) position sensor faulty signal(intermittent or permanent fault).

That code could appeared because of that loosened wire from a relay.It might touched the ground or some other wire on it's way while it was disconnected.

[jalwlb]

The engine runs fine and the transmission shifts flawlessly. The flashing yellow arrow which I have never seen before is gone and its appearance makes no sense to me, but I have read about it in other MVS posts about 850's that won't start. Hopefully checking this orange wire will help someone out in the future. It was a long process for me to find it.

[misha]

It seems that re-connection of disconnected wire,cured the code you had and made it to vanish.