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namao
Senior Member
Canada
89 Posts |
 Posted - 12/29/2014 : 10:42:21 AM
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| I am working on a 2004 3800 int school bus with a 2000 Allison automatic. I am trying to figure out how it is wired so I can locate the issue. I have no speedo. I have a code 141 in the ecm which indicates a open or shorted input on the vss lines and no speed indicated at the ecm pid.. According to international the two inputs are pin 39/40 on the ecm from the output speed sensor, then the ecm relays info to the cluster [volts, oil pressure, rpm and speed]. If you read the flow chart it says the sensor is on the right lower side of trany , on this 2000 Allison I see only the three on top. So I hooked up with my Allison software and there is no codes and all three sensors [input, turbine and output] register properly. Know looking at the Allison wiring diagram off the software it shows the tcm sending out a speedo signal. So I am not sure does the ecm get its vss input, off the tcm or is the tcm and ecm spliced together to the rear sensor or is there actually another sensor[ I do not think so not on the 2000 Allison model]. I am thinking I have a bad wire but would like some idea how its wired first before I get into it. Any input would be appreciated. |
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Fastback
Top Member
1500 Posts |
Posted - 12/29/2014 : 11:57:58 AM
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| Is it a CE or an FE bus? Oops I see you said it was a 3800? My fuzzy old brain does not recall them making 3800s in 2004? |
Why yes, the ORIGinal CHARGER is a Fastback |
Edited by - Fastback on 12/29/2014 12:00:04 PM |
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namao
Senior Member
Canada
89 Posts |
Posted - 12/29/2014 : 12:33:17 PM
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| I guess I should clarify its a blue bird bus body with a 3800 chassis, sorry should of added that. |
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namao
Senior Member
Canada
89 Posts |
Posted - 12/30/2014 : 08:05:10 AM
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| It is fixed, found a damaged wire above trany. Basically I started checking wiring underneath and the speedo started to work. I then found pins 39 and 40 on ecm and hooked up my vantage scope and had a pattern which changed with speed. Then I got under with some one watching scope and could actually narrow it down to above trany. removed floor plate and found wire broken in casing near connector for engine harness to trany harness. I believe the output speedo signal is from the tcm, it sends the signal directly to the ecm [the connector on trany was a two wire connector with one brown wire on the trany side sending signal], then the ecm sends the signal to the cluster along with rpm, oil pressure and voltage. thanks for taking the time to help, Roger. |
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04 int 3800 no speedo
