code 42 car runs bad real techincal question

[randymcc]

car stumbles and runs bad. went down flow chart and come to the part where it says put 12v source to pin D5 and resistance should go from under 200 ohms to over 8000 ohms. which it dosent change the resistance at all. next step is check est wire for short to ground and it is an open circuit when ign module disconnected. next check circuit 424 or bypass circuit for open and it is not. if it is not poor connection at module or faulty module.

O.K. well the module is brand new and the circuit shows 4.56v when the car is running at the ecm connector.So circuit must be good. What am I missing.
been fighting this problem for a month help please. have many other codes and they all lead like this. Been allover ecm connections and grounds and added grounds. Tried 3 ecms and pinned out all ecm readings for short to grounds, voltage, and excessive amps. All ecm readings are in specs that i have read.car is not in limp mode because i removed calpack.

 

[randymcc]

new crank sensor and balancer looks good. camshaft sensor looks to be set correctly

 

[pacecarta]

check the wires below the esc (passenger fender) , they tend to get rubbed through at the bolt heads into the fender

my problem with 42 was at first a bad ignition module , fixed that and then it returned about a year later , rechecked the white and tan est wires and they checked ,tried a new ignition module and even an ecm ,still threw code and stuttered went into bypass mode to the point one day i couldnt restart
,my trouble turned out to be EMI interference picked up in the DirectScan ribbon cable (i had connected it at the beginning of this year) , unplugged it and car started right up troubles went away
wrapped the ribbon cable in foil and grounded it no more troubles

also do you have any moisture on the ecm from a leak

try pulling out the white wire from the ecm connector and squezing it a little and reinstall to make sure it has a solid connection on the pin


check your plug wires and their routing , they are the main source of the EMI that can cause the 42 code to be thrown . replace them if they are old and try to route them away from the engine harness

 

[randymcc]

thanks for reply. car is still setting codes 34,42,44,55,53,51 but seems to run perfectly after fixing some ecm connector pins?

Any reason why except a bad ecm?

 

[Eric Stage I]

What scantool are you using? and what chip?

Eric

 

[randymcc]

i have an otc 4000 and scan master. I am using a yaklin ( i think that is the correct spelling) 8 postion thumbwheel.

 

[Eric Stage I]

I would ask Steve if maybe that thumbwheel is set up with the fast update code (which would make it throw weird codes on a OTC). Does it show the same codes with the scanmaster (what version scanmaster)?

Eric

 

[pacecarta]

as eric said if you have fast update code burned into the chip you may be reading ghosts because the mal function in the data stream is lost for the fast data which will now have SP(spark advance)and PW(injector Pulse width).
i have those #s (ill call them #s because they arent codes) in my SM at the MAL mode all the time with No SES light on dash . they show up even after an ecm reset . i get a couple then over time i have most of them ranging 30-55 , if you hook up directscan (or tlink) with a fast burn chip it will only show trouble codes if they are real , mine showed none on DS until the 42 popped up on DS and at that point the car had stubled and gone into bypass so it was a real code and the SES light on the dash was on.

OTC and other scan tools may not distinguish the data and show just as the SM shows but the paperclip method will retreive the codes stored if they are real.
BTW my SM is a 2.0 with a 2.1 update and chip is burned for 2.1 fast update so mine may be unique or the code for 2.1 may do the same on all 2.0 SM units

 

[randymcc]

thanks for the replies guys! the check engine light is not coming on now. I foxed the cam sensor which was rubbing he balancer and cleaned the and repaired the ecm connection. I just wish I knew what code was real and what problem I actually had?

That bugs me to not know about the fake codes and yes is does have the fast data. Oh well, now I wonder what was actually wrong with the car?