2001 Suburban: P0174, P0171, P0300, C0252, C0265, C0236

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Jediguy

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Hi all!

My service engine light has been coming on and then disappearing a few different times over the last few weeks in my 2001 Suburban 1500.

I stopped by the auto parts store and had them read the codes.

I have no idea if this is serious or not. I would be so grateful for an interpretation of what's going on and a best course of action to get things right with my truck.

The Codes are as follows:

P0174: Bank 2 System Lean
P0171: Bank 1 System Lean
P0300: Random multiple Misfire Detected
C0252: Electronic Brake Control Module
C0265: Electronic Brake Control Module Motor Relay Circuit
C0236: Rear Wheel Speed Signal Missing

It would be awesome if these were all issues I could fix myself.

Thank you for any and all input, your perspectives are appreciated.

Matt
 
Thank you for your response, Zora.

Those links sent me in the right direction.

After reading up on the error codes I did 2 things.

1. I cleaned the air filter, will likely replace it soon and sprayed the Mass Air Flow Sensor with MAF Sensor Cleaner.

2. I replaced the fuel filter, it definitely needed it, all the fuel was black coming out, this truck just crossed the 200,000 mile mark and I wouldn't be surprised if this was the first time it was replaced.

I believe that will help, only time will tell if P0174, P0171 and P0300 come back. My next fill up I'm also going to throw in a fuel system cleaner. Any recommendations? I never use one.

I still don't understand what to do about C0252, C0265 or C0236. I'll do some further investigating. If anyone has any thoughts on those error codes please do share.

That's my current update :)
 
any of the major brand cleaners is fine. Check for broken wires leading to the rear sensors.
 
Update:

  • Replaced Fuel Filter
  • Replaced Air Filter
  • Cleaned Mass Airflow Sensor
  • Used Techron Fuel System Cleaner on 1st Fill up
  • Been using Lucas Injector Cleaner with every fill up since.

Error codes persist after clearing the codes:

C0236
C0265
C0245
C0241
C0251
C0246
C0242
C0252
P0171
P0174
P0300
P0171
P0174

The ABS, Parking Brake and Service Engine Soon lights light up often and then disappear.

I am uncertain as to what is causing the misfires.

As far as the ABS and Parking brake light it looks the Electronic Brake Control Module needs some attention. From what I've researched it could just be a ground that needs a more secure connection. I'd like to try that before removing the EBCM itself and resoldering inside.

Only thing is I can't find the ground connection to frame for EBCM.

Can anyone help? I've looked all over the internet.

Of course, any thoughts on the whole scenario are greatly appreciated.

I'm really looking forward to having this truck in proper working order.

Thanks!
 
Hey thanks! I guess I overlooked some things.

There are two O2 sensors correct? Do I check them both the same way with a voltmeter? I assume they serve different functions so I don't know exactly how to go about it. I read the link you sent and watched the videos.

And the rear wheel sensors, is there an easier way to test those other than jacking up the car and taking the wheels off?

Thanks for your help, sensors are something I've never troubleshooted before so it's a new learning experience for sure.
 
the codes tell you which set of cylinders, P0171 has cylinder #1, P0174 is the opposite bank from #1, and point to the first O2 sensor, the one before the cat. Since both sides show lean start looking for a vacuum leak from a cracked, disconnected/broken hose.
if you can reach the wheel sensors to test resistance without jacking the vehicle up and removing the wheels do it.
 
Hi again,

This has been quite a lengthy conquest of getting my truck back in order as time and money allow me to work on it.

Update:

I replaced the coils thinking that would be a good idea but it didn't do much, oh well it couldn't hurt.

I also did the front brakes so at the time I tested the wheel sensors with a voltmeter and they were good.

I went to check the rear sensors and they didn't exist.

So I finally took it a shop and paid for the in-depth diagnosis. ( I wish I had done this months ago!)

For the ABS Light it turns out the EBCM is bad but I'll fix that another day.

The engine light causing the misfires and lean fuel condition turns out to be the MAF Sensor, they determined it needs replacing as cleaning was not the solution.

So in order to save $$$ I ordered the MAF Sensor from 1aauto for a fraction of what the shop wanted to charge and it should be an easy replacement.

Question is how do I reset the computer once the new MAF Sensor is installed?

The guy said it had something to with timing, which is above my mechanical comprehension.

But if it's just a reset it shouldn't be hard for an average person to do right?

The shop said it was something only they could do with their software and want to charge me $49.99 for...

Any ideas on how I do this myself?

Thanks again for all your help on this ever so long journey to get my truck back in order! :)
 
You can try disconnecting the battery but if that doesnt work you need a scan tool to reset it.
 
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