Check Engine light - MCI 102C3

Scott & Heather · March 21, 2017, 08:17:37 PM

Ditto what Cliff said. My bus will start and run for a bit before shutting down from a low coolant sensor

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JT4SC · March 21, 2017, 10:34:38 PM

After a frustrating 24 hours the folks at Valley Power Systems pluged in the diagnostic computer and the code said it was a faulty speed control sensor. We went on a test drive and the speedometer works fine but his hand-held diagnostic computer said we were going 0 mph.
They said its probably an issue with a sensor on the transmission. The transmission mechanic then came over, inspected the transmission and determined that the transmission was working fine as well. So they told me they didn't know exactly what was wrong, and that they would need to further inspect more of the bus to find the issue. He said in his opinion the bus was safe to drive on our trip, so that's what we did. We just got to the Grand Canyon KOA, and the bus ran great. We drove approx 400+ miles, everything looked, sounded and smelled fine. Only issue is I still have the check engine light on...

if anyone has any experience with a speed control sensor I'd love to pick your brain. It's frustrating the mechanics had the code but could not find the issue.

Thank you for your help!!!!

blue_goose · March 22, 2017, 08:57:29 AM

I have a 102C3 with a B500 transmission. The speed sensor has been one of my two problems with the bus. There are 3 speed sensors in the transmission. The one that is giving you problems is the one on the tail shaft of the transmission. If this isn't working you will not shift. If it isn't working like it should you will shift but show no speed. Now one has been able to tell me why, but I had the problem. Two years ago I replaced the sensor and it fixed the problem for 7000 miles. Last year same problem. I put a new plug on the wire going to the sensor and it fixed the problem again.
Ted at TKT told me that the plugs give lots of problems. He sold me a new plug with about a ft. of wire on it. I spliced the new plug on and so far everything is OK.
No one so far can tell me how the transmission can see the speed sensor and the odometer records miles, but it will not show speed.

JT4SC · March 22, 2017, 09:23:37 AM

Quote from: blue_goose on March 22, 2017, 08:57:29 AM
I have a 102C3 with a B500 transmission. The speed sensor has been one of my two problems with the bus. There are 3 speed sensors in the transmission. The one that is giving you problems is the one on the tail shaft of the transmission. If this isn't working you will not shift. If it isn't working like it should you will shift but show no speed. Now one has been able to tell me why, but I had the problem. Two years ago I replaced the sensor and it fixed the problem for 7000 miles. Last year same problem. I put a new plug on the wire going to the sensor and it fixed the problem again.
Ted at TKT told me that the plugs give lots of problems. He sold me a new plug with about a ft. of wire on it. I spliced the new plug on and so far everything is OK.
No one so far can tell me how the transmission can see the speed sensor and the odometer records miles, but it will not show speed.

Here is what doesn't make sense in my situation - the speedometer works and the tranny shifts at the exact speed it's supposed to shift.

luvrbus · March 22, 2017, 09:56:53 AM

Your transmission is probably a 700 series behind a 6v92 DDEC 11 I really doubt you have a World Allison like a B500 in your bus ,the 700 series ATEC transmissions are in a different world and place all of their own

blue_goose · March 22, 2017, 10:49:40 AM

The speedometer on your bus doesn't use the transmission sensor. I use a silverleaf as my speedometer, when the sensor was acting up it would record how many miles, but would not show speed.
Jack

luvrbus · March 22, 2017, 11:29:53 AM

If you have a 700 series Allison the scanner will not read the speed it has to be read at "maximum feature throttle interface" that connects the DDEC ECM to ATEC -1 ECO and it is a separate black box supplied by the manufacture of the bus ? what transmission do have without knowing we are guessing

JT4SC · March 28, 2017, 04:34:36 PM

Quote from: luvrbus on March 22, 2017, 11:29:53 AM
If you have a 700 series Allison the scanner will not read the speed it has to be read at "maximum feature throttle interface" that connects the DDEC ECM to ATEC -1 ECO and it is a separate black box supplied by the manufacture of the bus ? what transmission do have without knowing we are guessing

Hi everyone, we made it back from our trip, bus ran great, only issue was the check engine light. Luvrbus - I have confirmed the tranny is an Allison HT740.