Where is the ABS. ECU

[John Hennessey]

We have a 2003 Marquis Sapphire and need to find the ABS ECU to find the model number for the wiring diagrams. We tried pushing the button described in our manual for the codes and couldn't get it to blink a code. We had some brake work done at Boyer trucks in Minnesota and since then the ABS dash light has stayed on. It looks like the sensors are wired up so at a loss to be able to diagnose. Any thoughts as to where the ECU is located

[Gerald Farris]

John,
The ABS ECU is either in the LF electrical bay or inside the drivers left arm rest below the switches.

Gerald

[Mike Merchant]

John,
We had a similar experience last spring after a stop in Grants Pass for a tire wear problem. We were referred to Eugene for a frame straightening and as I got out on the freeway heading for Eugene I noticed the ABS light was on. Called the Grants Pass folks who stated it wasn't due to the front wheels being taken off, brakes checked, front end aligned, etc.
Pulled into the truck frame shop in Eugene and mentioned it to the service manager who knew immediately what the problem was, fixed it quickly at no charge.
The Grants pass folks had not reset the ABS sensors on the wheels. Apparently they have to be at a certain spot or the system defaults to the ABS light on. Simple fix, disappointing cause.
Perhaps that is all your problem is........                                                              Mike

[Bill Sprague]

Mine was built so there was about 1/8" less slack than needed.  If I went through a big enough dip, a sensor lead connection on the rear axle would pull apart just enough that it did not have electrical contact.  It looked plugged in, but was not.  It was difficult to reach.  The final answer was to create more slack in the connector.

[John Hennessey]

Thanks everyone for the info. Does anybody know of a reliable facility to look at the ABS system in Tucson or Phoenix?

[John Fearnow]

Inland kenworth off I-10 in Tucson got mine adjusted correctly.

John Fearnow
2002 pat thunder
Tucson

[Andy Clark]

'95 Patriot. Our ABS ECU is mounted to the underside of the coach floor on the passenger side just behind the front axle line. You have to squirm under the coach and look waaaaay up to see it.

HTH.

Andy