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1998 Pontiac Sunfire, codes 0172 and 0404


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chrisser
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Nov 5, 2011, 9:43 AM

Post #1 of 9 (4191 views)
1998 Pontiac Sunfire, codes 0172 and 0404 Sign In

1998 Pontiac Sunfire, codes 0172 and 0404. I have replaced the egr valve and the o2 sensor. The same codes keep returning. What else should be looked at?


Discretesignals
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Nov 5, 2011, 9:46 AM

Post #2 of 9 (4189 views)
Re: 1998 Pontiac Sunfire, codes 0172 and 0404 Sign In

Which engine are you dealing with? 2.2 or 2.4?





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chrisser
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Nov 5, 2011, 10:04 AM

Post #3 of 9 (4171 views)
Re: 1998 Pontiac Sunfire, codes 0172 and 0404 Sign In

2.4


Discretesignals
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Nov 5, 2011, 10:29 AM

Post #4 of 9 (4166 views)
Re: 1998 Pontiac Sunfire, codes 0172 and 0404 Sign In

P0172 is fuel trim rich code. Means the PCM is seeing a rich condition and is trying to compensate by leaning out the engine.

You really need an enhanced scan tool to monitor fuel trim readings at different rpms, coolant temp, injector pulse width, MAP sensor voltage, O2 voltage, loop status, etc. to diagnose this kind of problem

Some things that could cause that are:

Restricted air filter
High fuel pressure
Leaking injector
Leaking fuel pressure regulator on vacuum side
MAP sensor vacuum hose disconnected or rotted off
Stuck rich O2 sensor

Vacuum leak, unless the leak is huge, will make the engine run rich on those because it is a speed density based injection system.


The P0401 EGR Flow insufficient could be caused from:

Restricted or carboned up EGR feed or outlet passages.
Wiring problem for EGR ground, power or position circuits.
Faulty PCM not sending power when EGR is commanded.

It's possible the MAP sensor could be a problem, if it has no vacuum input, because part of the EGR diagnostics uses the MAP voltage to determine if the EGR is flowing or not.

Once again a scan tool with bidirectional capabilities to activate the EGR valve and monitor isn't position would make diagnosing this problem a whole lot easier.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Hammer Time
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Nov 5, 2011, 10:49 AM

Post #5 of 9 (4158 views)
Re: 1998 Pontiac Sunfire, codes 0172 and 0404 Sign In


Quote
The P0401 EGR Flow insufficient could be caused from:


Put the glasses on DS. It's not a 401



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Nov 5, 2011, 10:52 AM)


Discretesignals
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Nov 5, 2011, 11:20 AM

Post #6 of 9 (4151 views)
Re: 1998 Pontiac Sunfire, codes 0172 and 0404 Sign In

Oops..once again I try to make the perfect post and screw that up...LOL.

P0404 means the PCM is seeing a difference between the desired and actual position of the pintle in the EGR valve.

You'll still need a scan tool to see what the PCM is seeing as a pintle position and to command the EGR to check the position sensor's voltage changes.

Check the wiring really good at the EGR valve. Looked for broken wiring in the insulation at the EGR electrical connector. If you have a meter check for 5 volts on the grey wire with the ignition turned on with the connector unplugged from the valve. You should see close to 0 ohms on the black wire. You should see 0 volts from the PCM on the brown wire.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Nov 7, 2011, 8:53 PM)


chrisser
New User

Nov 5, 2011, 1:19 PM

Post #7 of 9 (4140 views)
Re: 1998 Pontiac Sunfire, codes 0172 and 0404 Sign In

Hold on while i check


chrisser
New User

Nov 6, 2011, 10:51 AM

Post #8 of 9 (4121 views)
Re: 1998 Pontiac Sunfire, codes 0172 and 0404 Sign In

Here's what I got:
Reference negative battery terminal, ignition on
red - 12v
Grey - 5v
brown - 0v
Black - 0v
Black/ white stripe - 0v

Black - 0ohms

Now what?

Thanks


Discretesignals
Ultimate Carjunky / Moderator
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Nov 7, 2011, 8:52 PM

Post #9 of 9 (4089 views)
Re: 1998 Pontiac Sunfire, codes 0172 and 0404 Sign In

You have gone as about far as you can. You need a scan tool that can command the EGR valve to check pintle positioning.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.






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