Throttle Position Sensor Defective and No Longer Available

[Ron_H]

Our 2005 Newmar mountain Air 4301, on a Spartan Mountain Master chassis has a defective TPS and replacement parts are no longer available, according to Spartan.

Spartan has provided me with complete replacement throttle assembly, which Spartan says is compatible, but a local shop was unable to install it as they say it's incompatible. Spartan says it should plug into the existing throttle cables but the shop has traced the wires all the way back to the bulkhead connector and the loom does not contain any connectors similar to those on the new pedal assembly. Spartan then said, if the shop is unable to locate the connectors, which they insist are there, they can splice the wires from the new pedal into the existing harness. The shop looked at doing this until they discovered that the replacement pedal assembly has only six wires whereas the OEM throttle pedal assembly has seven wires.

I have used this shop before and I am confident they know what they are doing and they seem to be going out of their way to assist us.

I've spent over $450 for the new pedal assembly and over $300 on shop time (they only charged me for about half of the time they spent on it) and there is still no solution in sight.

I am turning to this forum for feedback from anyone else familiar with this type of situation and/or possible remedies. A coach without a reliable throttle can't venture very far.

Background:
Two years ago, while in Newfoundland, the engine warning light and buzzer came on and I had limited throttle and power. While attempting to drive to the nearest town, 60 miles away, the warning went off and on several times, and then it all settled down to a normal operation about 15 minutes later.

At a repair shop, the engine codes indicated an error with the TPS. A call to Spartan advised us of the non-availability of the TPS and a workaround by replacing the complete throttle assembly. Due to the long wait of getting it to Newfoundland and the fact that it was then working again, we opted to put off the throttle pedal assembly swap.

Two years later, the engine alert and TPS symptoms had only occurred twice, each for a limited period of time. Then, a couple of weeks ago it occurred again, while in the mountains, and continued to go off and on for the remainder of the day until we reached our final destination.

I phoned Spartan, ordered the replacement pedal assembly and book shop-time for the replacement. After two days in the shop (very inconvenient for full-timers) and several calls back and forth with Spartan, the shop has given up saying it won't work. As it is the weekend now, I have to wait until tomorrow to talk to Spartan again.

All feedback and suggestions are appreciated.

[TJ]

Well, if it was me, I'd try to get the coach into the nearest Spartan service center (many Cummins service centers also are Spartan service centers) and let them find the solution.

TJ

[Ron_H]

That would normally be a good option but I have had work done by the local Spartan shop in the past and it turned out to be a very costly and unsatisfactory experience. As they are only an Authorized Spartan Dealer, not an actual Spartan operation, I don't think it would get us any further ahead.

Thanks for the suggestion.

[Qwert66]

There's a 99% chance it's a Williams Controls TPS.
Its a hall effect sensor for 2 purposes.
"Not in Idle", and "Give it some level power"

When the 2 conflict then it de-rates the engine speed to basically idle, regardless of throttle position and results in a fault code. This sensor very rarely if ever fails as it's not contact style. Ask the service shop when they last changed one??

My bet on your situation is you have a short to ground on one of those wire harness leads between the pedal and the ecm in the back. On ours there was/is a electrical connector in the position sensor wires appx 12" from the pedal below the floor viewable by pulling out the genny and looking up where the pedal would be.

I changed our position sensor (Williams Controls appx $65) and it didn't fix the problem. Electrical Tech at the shop while watching the fault codes and wiggling the wires found that our short was from the end of a sheet metal screw that mounted the cb remote box under and to the right of the steering column.

An alternative fix was going to be running all new wires from the pedal back to the ecm but luckily the problem was identified/fixed prior.

I wish you the best.

Ours was a $260 2hr labor + $65 part (now a spare) = $260.00 total plus my time to change the sensor.

[Ron_H]

Thank is good information, thank you.

I'll bring this up both with the shop and Spartan tomorrow morning. At this point, I had assumed the shop in Newfoundland had correctly diagnosed the problem but it's likely a good idea to take a step back and confirm their findings.