[Jeff]

I’m very glad to hear you got her going again! Prevost never did email me the diagrams after several attempts on their website with different browsers and email addresses. It wouldn’t have helped you anyway as it turned out.

“Did the bad wiring harness also short something in the ECM?”

That is very possible, I would even say likely if you could push on the harness and change how the engine runs.

Interesting how you had a fuel pump and an ECM problem, but you were able to start it from the rear!

[John]

I have posted on here before that I have experienced sporadic problems with the Jake kicking out during a run. Maybe 15 times in 10.5 years of ownership the Jake would be working in the morning and stop working at some point during the drive. Most of the time, it would only work again after I had parked, shut down and then cranked again.

The frequency of this sporadic problem picked up considerably the last 4-5 months.

I mentioned this to Prevost and Mid Coast in Houston when they were diagnosing and replacing the fuel injector wiring harness. Mid Coast was pretty confident that the wiring harness would rectify the issue.

I thought that it had until about the fourth day I traveled after the wiring harness replacement. On that day, the Jake Brake quit after a few hours. It was working on the next start up.

After the ECM was replaced last week, I was doubly sure the Jake would be back to stay. Today, on my third day driving with the new ECM, the Jake did not work at all. Ugh!

What else would cause this?

Davy

[Archived]

Davy, sound like you have a bad TPS (throttle position sensor). My coach was doing the same thing, replacing the TPS solved the problem. Williams Controls 531402 ordered from Prevost $127.

[Archived]

Thank you. I have questioned that in the past. I appreciate the information.

Davy

[Davy]

We were traveling last week and the Jake quit. Rather than turning off the engine and restarting, we unplugged the TPS and then plugged it back in. The Jake was reset and worked the rest of the day.

I ordered the TPS from Prevost and it comes with a new wire included because the plug is different on the new TPS. When I saw that, I remembered someone writing about that.

We are covered up this week so no time to tear into it. Can anyone tell me where the wire goes and how difficult it is to change it?

Thanks,

Davy

[Archived]

When I had a TPS issue the wire from the pedal inside the cabin, went through the floor and the connector was at the underside of the floor accessed by dropping the front bumper. That was on an 87 coach so yours may be different.

[Larry]

Thanks, Jon.

[Bill]

Update on the Throttle Position Sensor and the Jake. I ordered the TPS from Prevost and it was in the neighborhood of $130. It was the part number given to me a few posts up and came with a new harness.

It would have been a very simple change if not for the harness and it was not too bad even with the new harness. Thankfully the guy the drilled the hole in the floor for the original harness behind the accelerator pedal was an overachiever. If the hole had been just big enough for the original plug, I would have had to enlarge it.

My wife fished it through the floor, I plugged it in below and secured it with wire ties. I went above and installed the TPS, plugged in the new harness and strapped the wire.

I have driven 13 days and a few thousand miles and the Jake has worked every single time it has been called on. Yay!

As a refresher, the harness had been changed and the Jakes inspected as part of the major repair in January. The ECM (Engine Computer) had been changed as part of the second repair discovered and detailed in this long thread.

The Jake would still kick out and replacing the TPS solved it!

Davy

[Bernie]

Thanks for the follow up Davy.

[Rudy]

This thread has been all over the map, but I do have a little to add to it.

Recap:
In January I had the engine removed to replace the wiring harness to the fuel injectors. I had them replace the fuel injectors while they were in there.

Two weeks later the ECM went down. In the process, we changed the fuel pump (Also Bad), cam sensor, crank sensor and ultimately the ECM.

A few weeks later I changed the Throttle Position Sensor and that cleared up a long term intermittent Jake problem.

There is one thing that I do not think I mention. When Brad, the mechanic that helped me so much in Mississippi, remove the crank sensor, there was a very small sliver of metal on the magnetic end.

That was very concerning to him and his gut reaction was to pull the engine and rebuild. I could not wrap my head around rebuilding an engine that was running good and smooth, but I did not discount his cautious approach.

After talking with Jeff Rowe, we came up with a plan. Brad changed the oil before I left Mississippi. It had only been 1700 miles since my last oil change, but the engine had been out, the top end opened, the fuel injectors were replaced and all the other drama I have described.

The oil sample from the change in March and also the sample I had from the January oil change 1700 miles before were taken to Puckett Machinery in Jackson Mississippi. The samples were processed and sent to their lab and the reports came back good.

We resolved to either pull a sample or have the oil changed at about 7500 miles and analyze the oil then. With that information, we could proceed.

I found myself in the northeast at 7500 miles and could find no place to get the oil changed or a sample pulled so the sample was taken from an oil change last week at about 9900 miles.

I received the results today and all looks very good.

Whew! I am very thankful.

Davy