ABS light after hard acceleration

[mwilsonsr58]

I have a 1998 XJ with 6 cyl. And AW4 automatic that run and drives perfect during normal driving. But during hard acceleration (foot to the floor) when transmission shifts from 2nd to 3rd the tach bounces to 100%, the ABS light illuminates and the transmission goes to 3rd and no longer shifts automatically. I can manually shift the transmission and it drives fine. When I turn of vehicle and back on the light clears and all is fine until I accelerate hard. Please don’t recommend that I remove the ABS, I would rather fix the problem. My code reader will not show the ABS code. Looking for ideas before I go to shop to get ABS code read.

 

[Tim_MN]

The issue is not likely to be ABS related.

I would concentrate on the transmission symptoms and begin transmission diagnostics.

 

[lawsoncl]

ABS and the trans computer really aren't related. Hard acceleration makes me think damaged wiring, exacerbated by bad motor mounts letting the wiring flex or touch something like the exhaust manifold.

Can you trigger this in the driveway by holding the brake while you gas it in either forward or reverse?

 

[mwilsonsr58]

Motor mounts and rear transmission mount are all good. I replaced CPS last year with non OEM unit. I leaning toward a problem with it causing the tach to bounce. My understanding is that tach signal comes from CPS. Not sure of correlation between CPS and VSS. I know if VSS speed is a couple of mph different than any wheel sensor it will set ABS code.

 

[RCP Phx]

The tachometer is driven by the PCM.

 

[lawsoncl]

I think you're losing power somewhere, and the tach bouncing is perhaps the dash resetting on poweron.

 

[Tim_MN]

Improper shifting allows the engine to rev too high. Mismatch between rpm's, VSS and/or ABS sensors likely is the root cause for the ABS light.

The dash does not re-set.

Diagnose the shifting/reving symptoms. I would look at the TCM, the shift solenoids, and their related wire plugs and wire harnesses.

Temporarily disable the ABS by pulling the fuses or relays and see if the transmission symptoms persist.