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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 2621
Experience:  I worked on all types of equipment semis,forklifts,farm,ect.
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I'm trying to help my husband He has a Kenworth with Detroit

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I'm trying to help my husband He has a Kenworth with Detroit engine. Truck will be running fine and then speedometer goes to zero something about 1500 rpm and check engine light comes on. He went to a Kenworth dealer but they don't work on Detroit engines anymore
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Heavy Truck Mechanic I'm going to connect you with knows all the tricks and shortcuts.
Customer: thanks
JA: Anything else you want the truck mechanic to know before I connect you?
Customer: no

Hi, my name is ***** ***** for your question.I'm reviewing your question now, and will post back with your reply ASAP.

When the engine looses speed signal it de-rates engine to 1500 RPM to keep guys from bypassing any speed limiter settings programmed into ecm

This does tell us it's a signal issue from the VSS (vehicle speed sensor) The sensor is located on back of transmission by driveshaft and can be replaced easily (replace VSS)

Just remove and install a new sensor,, screw new sensor in all the way then back off 1/2 turn and lock down nut

This should take care of check engine light and keep engine from not going above 1500 RPM

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Customer: replied 1 month ago.
He already did that and changed speedometer/odometer head. He did tell me it's a T2000

Make sure yoke on back of transmission is tight,, if loose it allows drive ring for speedometer to slip so sensor does not read correctly

The only other thing would be a wiring issue from VSS to engine computer (ECM)

It's a two wire harness he can follow from VSS to ECM and check for any rubbed out spots along frame, transmission, or engine or corrosion in plugs

Repair, clean, or replace as needed

If he wants to do a phone call I can send a offer for extra service just let me know if that would help?

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