When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Fixed an interesting issue with drive by wire throttle.
I get into the car the other day and it starts up fine. I touch the throttle and nothing happens. I floor it and nothing happens. It's not "limp mode" but zero mode. I shut it down and restart it but still nothing. It starts right up and idles fine but that's it.
Pulled codes and found a bunch of codes referring to pedal position sensor voltage. Everything I looked up referred to a bad pedal sensor or throttle body motor but they seemed to test out fine. Turns out it was something more simple.
There's a soft plastic plug that acts as a stop for the upward travel of the pedal. When you let off the pedal it's upward travel is limited by this plug. The plug lives at the top of the pedal assembly up against the firewall. You have to remove the assembly (two easy bolts) to access it. Well, this plug degraded and I found it in pieces on the floor under the pedals.
As it turns out this plug is more important than just softening the stop of the pedal. Even though it's only 4 mm thick, its position acts as the starting point for where the switch starts reading voltage. The pedal sensor works by increasing the voltage as the pedal is depressed. It starts at a specific voltage and maxes out at a specific voltage. With the plug gone the sensor overextends in the closed position and reads a lower starting voltage. The computer sees this and shuts the whole system down.
The fix was easy. I just happened to have a bolt with a 4mm thick head and simply installed it in place of the plug with a nut on the back. That's a bit thinner than most bolt heads but I would have ground one down if necessary. I had to cut a little off the threads but there's plenty of room behind the assembly to fit it. I had to clear the codes before it would give a throttle response but once did that it worked perfectly. I can hear the pedal arm hit the bolt head but it's not noticeable when driving even with my manual shift.
That makes all 3 pedals that have given me issues with the rubber stops failing.
*The clutch pedal arm has a rubber stop that presses a switch at the bottom of its travel. That's the switch that lets it start when the clutch is pressed. That one degraded years ago. With that gone the switch plunger goes through the hole in the arm and it doesn't know you're depressing the clutch pedal. You get no start with no codes.
*The brake pedal arm has a plug in it that presses a switch to turn off the brake light when the pedal is at rest (foot off brake). When that plug degrades the plunger goes through the hole in the arm and leaves the brake light on all the time. Obviously that'll kill the battery. On drive by wire cars the brake light switch also cuts the throttle response by about 1/2 throughout the entire range. It doesn't throw codes, run rough or refuse to rev. It feels like driving an under powered 4 cylinder car that's operating properly.
* Now this issue with the throttle.
Nissan should have avoided using the plastic/rubber and gone with metal. Maybe and a thin coat of rubber if they wanted to soften the feel. At least when the rubber breaks down the car would still run.
The ex wifes 2000 did it with the brake pedal too. Drained her battery.
I do live in a warm climate but the car has always lived in the garage at home and had a sunshade and cracked windows when parked out.
It's something that might be good to check. If you poke at them they might be crumbling. It's an easy thing to handle proactively.
Yeah the little plugs that contact my brake and clutch switches got crumbly on me a few years ago, but I hadn't looked at the accelerator pedal one. Is there an audible metal-to-metal sound now when you release the accelerator with the bolt in place of that rubber stopper?
There is a sound when the pedal is released. It's obvious if I'm playing with it but I don't notice it when driving. In a quieter car it might be more noticeable.
If I were doing this for someone else I would take a strip of rubber, maybe from an exhaust hanger, and attach it across the whole back plate with a few screws. I can think of a couple other ways to do it too. This was just what I had on hand at the moment and it happened to be the perfect thickness.
The plug fragments were brittle enough I could crumble them. I was lucky it let go sitting in my garage instead of somewhere out on the road.
it happened to me. Nissan will try to sell you a new pedal assembly cause the parts catalog doesn't show the green rubber piece as an available part but it's the same as the one for the brake and clutch.
11-20-2023, 08:32 AM
