1998 code P1518 TAC Module,Reduced Power,Won't Accel

by Jack
(Old Saybrook,Ct.)

Hi,I can not solve the problem with my 98.Has codes P1518 TAC Module and P1571 Traction Control and the Reduced Power message and runs terribly.I did some research and saw that 97 and 98's had known problems with TAC modules so I figured that was my problem and tried to buy a new one but found that they were unavailable (nationwide back order)so I settled for a(supposed)good used one. Upon removing the old one I saw the part number was 25319443 like it had already been changed.(I don't remember what the part number of the original problem modules was but I know this was the updated number). The part number of the module I bought is 12578953 which is supposed to work as well as a couple of other part numbers.In any event,the problem is still there.Next,I checked connections at the gas pedal and TAC motor and the harness to the TAC motor.Checked and cleaned PCM connectors.Checked and cleaned engine and chassis grounds.No change.Next I followed the Alldata test procedure chart for code P1518 checking for voltage and continuity.All tested good until step 18 where it asks if there are 0 volts at the serial data circuit at the TAC module 16-way harness connector.I have 4.0 volts like I had back in a similar test in step 13 where they asked if there was 0-4.5 volts at both serial data circuits.Not sure if I installed a faulty module or what I'm missing. Any suggestions or advice would be greatly appreciated.Thank you,Jack.

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