Check Engine light code help

[sohc1996]

Hi guys!

My check engine light came on today and it came up with two different codes, P0138 and P0172. The car seems to be running fine with no drivability or performance issues. It's a 2004 Cruiser 5 speed. It has an extended warranty so I'll probley end up taking it to the dealer sometime this week but I wanted to some peoples opinions here before I paid the $100 deduct.

I had the codes ran at autozone and the guy there said it was most likley the Oxygen sensor, the down stream one, with the 2 codes that came up. The car only has 32,000 miles on it so I figured it was a little soon for the oxygen sensors to be going out. Has anyone else had these codes come up and what was the problem? Any other ideas, tips, or suggestions would be greatly appreciated. Thanks in advance!

Joe

[CREWZIN]

It looks like your gonna need further diagnostic work to pin point the problem.


P0138 O2 Sensor Circuit High Voltage (Post Catalyst)

P0172 System Too Rich

Oxygen sensors can set trouble codes for various reasons. An open sensor wire can set trouble codes. If a sensor stays lean or rich for a long period of time, lean or rich codes may set. In either case, the sensor may be at fault. Before condemning the sensor, there are some very important checks that should be made.

For continuously rich O2 sensor readings:

1. Check the fuel pressure. High readings will cause rich conditions.

2. Leaking injector(s) will cause rich exhaust.

A leak down test and/or a power balance test can usually reveal the leaker.

3. A contaminated or malfunctioning canister purge system can very easily put uncontrollable amounts of fuel into the intake manifold. Simply disconnecting the vapor hose can reveal this as your problem system.

4. Check vacuum to voltage readings at the MAP sensor. A low MAP output will cause a rich ecu reaction. (Don't forget vacuum readings again!)

5. A false tps signal can cause the system to go rich if the Ecu sees a high tps output. Check tps readings at idle and for a smooth rise to wide open throttle.

Remember that the O2 sensor can help you simplify your diagnosis and help you avoid frustration!

[wlauren15]

i too had the guys at auto zone run my codes and was told it was my oxygen sensor... will this effect a smog check due to the factt hat my check engine light is now on? and if so how easily is it replaced?

[CREWZIN]

The 02 sensors can be changed by the backyard mechanic without too much trouble. First you have to know the code that AZ pulled as you have two sensors (forward and further downstream). As far as your emissions check, I can't answer that. We have no emissions check or state inspection in Florida.

[the93rdkid]

Wow, Crewzin. From what I've read of your posts, you seem to be the PT god! I feel stupid asking this question. My 04 Turbo's check engine light comes on occasionally. When it does, car loses power and lurches. If I accelerate slowly, I can manage to drive ok. Here's my stupid question: where do I find the codes that everybody is talking about?

[CREWZIN]

Originally Posted by the93rdkid

where do I find the codes that everybody is talking about?

On the the top this Tech & Performance section of the forum there are "stickies" that are for information. There are two of them that you need to look at. One is entitled "how to retrieve fault codes" and the other is "error codes".

Find the fault and look up the code. If the code isn't clear,come back here and ask for help.

I just happen to be around on the forum a heck of a lot so I see the new posts first. There's heck of a lot more knowledgeable people on this forum than me.

[Travis2k7]

Originally Posted by sohc1996

Hi guys!

My check engine light came on today and it came up with two different codes, P0138 and P0172.

I had the codes ran at autozone and the guy there said it was most likley the Oxygen sensor, the down stream one, with the 2 codes that came up. The car only has 32,000 miles on it so I figured it was a little soon for the oxygen sensors to be going out. Has anyone else had these codes come up and what was the problem? Any other ideas, tips, or suggestions would be greatly appreciated. Thanks in advance!

Joe

I got the same P0138 code around 46,000 miles and it was the downstream O2 sensor... ordered a Bosch replacement from Autozone for $25, changed it out, reset the computer and all has been well since with no codes returning.