360 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:

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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.

 

Ricambia. You have to know if you have a black plunger or not. That makes a difference on the exact part. I had a black plunger.

https://www.ricambiamerica.com/334064-brake-pedal-switch-bosch.html

The picture shows a blue switch but the one they sent me was white just like the original.

 

The "simple" way to install a brake light switch:
Remove the old one.
Remove the connector from the old one.
Attach the connector to the new one.
DEPRESS the brake pedal with one hand.
Install the new switch using the other.
RELEASE the brake pedal.

The ratcheting action of the switch automatically adjusts when the brake pedal is released. Nothing more is needed to be done and it will always be right.

If the plunger has been "adjusted" prior to installing it (by pushing it in manually), then the plunger has to be pulled out again before installation. Some models of these brake light switches may not allow the plunger to be pulled out without destroying the switch.