I have read a lot about the "Code 42" problem, but my 88 Pontiac firebird 5.0 TPI is still giving me the code after check/change parts.

First i checked all connectors and wires from the ECM to the ICM and everythings is fine. The wires were not broken and no wire to ground. The checklist said "ECM faulty". Ohmmeter CKT 423 = 375Ohm, CKT 424 = light off, CKT 423 & CKT 424 = 6K23, faulty ECM.

A few months ago i ordered a few parts from Rockauto, also a complete distributor, an ignition coil, spark plug wire set and sparkplugs. Yesterday I build it in and set the timing (deg 6 adv) with disconnect/connect the bypass (brown wire). After disconnecting the battery for half an our i started the engine, there were no strange sounds and it was running ok, but still comes up with code 42 after a few seconds.

I also have read about the knocksensor, although that would be a Code 43. Is it possilbe to test the knock sensor with a resistor to ground to see if the SES goes out? Is there something else i could try to find the problem? I can readout the ECM with "TunerPro RT", but which values do i have to look at to find the problem?

Hope someone can help me. Tnx.

 

Iirc the ks should ohm out at 100k for tpi maf.
you can measure the resistance at the esc pin e to ground this is a dark blue wire.


http://www.chevythunder.com/est_code_42.htm

 

I located the ESC and the resistance at the white wire (schematic from Chiltons) to ground is 150k. Is this to high or is this acceptable?

 

Seems alittle high, but since you are not battling a code 43 and the code isn’t throwing during forced knock test. You should be fine and should focus on the error 42.

 

Ok thank you for your help.

This week i have the possibility to test it with another ECM, maybe that will solve the problem. I will keep you up to date

 

Just to add on to what TP has posted (I like the simplified flow chart).

Here's the Code 42 pages out of my '87 Camaro FSM.

 

Today i tested another ECM with my own memcal and no error-codes! The problem was a faulty ECM.

Thanks Tuned Performance & paulo57509 for your help.

 

Glad it was a easy fix