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Code P0042

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Old Feb 8, 2008 | 01:57 AM
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Default Code P0042

Hello, I need advice on what to look for that code on a 93 Firebird V6 3.4L

Car takes 20L to do 100km ...
Sometimes when idleing, RPM jumps from 400 to 900...
DTC code P0042

Thank you
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Old Feb 8, 2008 | 10:06 AM
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oxygen sensor?
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Old Feb 8, 2008 | 01:41 PM
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Im not sure on the Computer O2 Sensor says input jumping from 75 to 500. Don't know if it's good.

When reading codes, it said P0042 Ignition System
and on internet I get this :
P0042 H02S heater control circuit (Bank 1 sensor 3)

Wich one is the good one ?

Thank
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Old Feb 8, 2008 | 02:03 PM
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My friend says this code for that model indicate the car is running in System D wich is like "emergency ride". He says it runs Lean, and a ground is faulty somewhere. Probably the Ignition switch ground since the code reads it.

Anyone whos where its located ? The Ignition switch's ground on a 3.4 1993 Firebird V6

Ty
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Old Feb 8, 2008 | 02:39 PM
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On shoebox's obdI code list 42 is "Ignition Control (IC) Circuit (shorted or grounded circuit)" If you haven't already I'd check for a blown fuse somewhere, might help you nail down the circuit at least. 02 sensors are usually numbered from front to back standing at the radiator looking back, so my guess is if you have 3 it would be the one furthest back. Couldn't find a 3.4 diagnostic chart for codes, but there's got to be one out there somewhere. Sorry not much help....could be the ICM itself or just a wiring issue.
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Old Feb 8, 2008 | 03:03 PM
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Well since this code started to appear after I installed an Alcoolmeter (yeah I know im dumb ok no more joke : ) ). I think they missed a wire or something like that. Gotta check their wiring but since I can't play with it I'll call them on monday.

I have 2 O2 Sensor both seem to be ok. jumping from 75 to around 400~500 as the computer reads them.

Do you know where the PCM is located ?
Thank

EDIT ::
Fuse in Door seems to be ok,

Last edited by Mitchell22; Feb 8, 2008 at 03:22 PM.
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Old Feb 14, 2008 | 10:48 PM
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Hi guys,

can anyone tell me what is the grey wire on the ignition coil's plug (the largest one with the white tachometer wire) is used for ?

The guys at the garage plugged something on it, I think they wanted the tachometer and if Im right the good wire would be the white one. I think this one is used for ignition firing control.... Am I wrong ?

Firebird 1993 V6 Manual 3.4L
Grey wire on the ignition control plug on the coils.

Thank
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