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Accelerator Pedal No Response (Solved)

2001 gated 360 Spider, 18k miles. Stock everything except muffler.

I started the car like normal, everything seemed fine and drove it to the end of my road with low RPM's, as normal. By the time I got to the end of the road, the car had some temperature so I started driving normally. About half a mile from that point, I gassed it to get around a truck parked on the side of the road and then let it coast down to the speed limit.

At that point, the accelerator stopped working. I'd press it and nothing. Car was idling fine but no throttle response. I pulled off at the first right and suddenly, the pedal worked again, for a moment. Then it stopped responding. I turned around and started back home. No pedal. Luckily, it's a short ride on a 35 mph road, so idling along in 4th gear (about 15 mph) wasn't too much of an issue. I kept trying the pedal and nothing.

I turned down my road and drove the 1/2 mile to my house in 4th, idling. There's a pretty good but short hill right before my garage so I was a bit concerned the car wouldn't be able to idle up it and stall. Luckily, as I turned to go up that final hill, the pedal came back for just enough time to get me over the hill and into my driveway.

Made it back in and no pedal.

I had no CEL's or other indications that anything went wrong on the dash.

The first thing I did was read the codes:


The first code, P0571, was one I'd seen before. Bad brake light switch. I had the replacement part for that sitting on my workbench. Didn't seem likely that it was the problem. I researched the other codes and they seemed to indicate the accelerator potentiometer might be the problem.

At this point, I texted my Ferrari tech buddy with the symptoms and the code page. His first thought was that one of my throttle motors had died. He gave me a quick and easy test to do which involved pushing the throttle plate and seeing if there's a difference in the tension between the two. A dead motor might show as a difficult to push throttle plate.

I texted him back that all seemed fine with the throttle motors. He asked me if I had ever changed the brake light switch, if not, do so.

That made sense since the code had appeared again. I have no idea what the fault tree looks like for the ECU program but it does seem to care about the brake light switch for many reasons. In the F1 models, a failed brake light switch causes a lot more havoc and a "slow down" indication. I have a gated model so none of that is in the path. Still, there's the ABS system and who knows what happens in the code for gated models.

I changed the switch, a two minute job (careful: DO NOT play with the plunger), cleared the codes and gave it a quick test drive. The weather was closing in and it was about to start raining. I zoomed it back and forth on my road, which runs about a mile, and had no problems. I even ran it full throttle to redline a couple of times once it got up to temperature. No codes.

When I went back into the house, my wife commented that some nut was racing up and down the road making all sorts of noise. Oops. Well, it was the daytime and a lot of the leaf blowing equipment makes more noise than my F car at 8500 RPM's. No apologies...

I did a postmortem on the brake switch. It has two independent switches. I assume the brake code gets thrown when those switches disagree. The contacts on both switches were obviously pitted and burned from nearly 20 years of usage. The new brake switch was less than $30 including shipping.

It was about a week before I could do a proper test drive. Did that today. All good. No codes.

So either the problem magically disappeared for now, or it was caused by the faulty brake switch.

Update:

I found out something interesting regarding the way the accelerator works on a gated 360. If the brake is pressed, the accelerator pedal becomes inoperative. I don't know why this would be since it could be a tactic to press both the brake and gas pedal at the same time. Perhaps in sport mode it doesn't do this. Haven't checked.

So since this little tidbit has been revealed, the reason why I had no gas pedal action is because the system thought the brake pedal was actuated. That's why fixing the switch also fixed this issue because the brake switch must fail in the ON position.

Lots to learn about this car.

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