Check engine light codes

[Xtreemjedi]

Hey guys, I bought this 2003 Suburban Z71 4WD  about a month ago. It had many check engine codes but it runs and drives great. Can anyone help steer me in the right direction as far as getting some of these fixed? I know sometimes having move than one code can narrow the options of what the root cause is so I will post all of them:

 

U1000-Class 2 data link malfunction

U1255-Class 2 communication malfunction

 

C0300-Rear Propshaft signal circuit malfunction

C0305-Front propshaft speed sensor system malfunction

C0306-Motor A/B circuit malfunction

C0321-Transfer case lock circuit malfunction

C0327-Encoder circuit

C0359-4LO discrete output circuit malfunction

C0374-General system malfunction

C0379-Front axle circuit malfunction

 

P0141-Oxygen sensor heater circuit bank 1 sensor 2

P0154-Oxygen circuit activity detected bank 2 sensor 1 intermittent

P0155-Oxygen circuit heater circuit bank 2 sensor 1

P0161-Oxygen sensor heater circuit bank 2 sensor 2

 

I think P0141, P0154, P0155, and P0161 just means I need to replace all 4 O2 sensors? or could it mean something else?

 

Also the "service 4wd" and "rear access open" messages on the dash. It seems the truck thinking the rear access is open is why 1:the rear wiper won't work 2: the interior lights will only come on when I push the dash button but not on extt/entry and 3: I can't lock the doors while the truck is on.

 

The U1000, found online it probably DOESN'T mean the PCM is bad, possibly a bad ground, but I also have the U1255, IDK if they are related.

C0300 says it could commonly be four-wheel drive switch or actuator failures.

For C0300 and C0305 I found this page: Chevy bulletin

C0306 youtube-bad ground-I am going to go try and do this tonight if weather permits.

 

 

 

[sefiroxx]

Sounds like bad wiring harness or ground. Something may have kicked up and nicked something.

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[carnau]

8 hours ago, Xtreemjedi said:

Hey guys, I bought this 2003 Suburban Z71 4WD  about a month ago. It had many check engine codes but it runs and drives great. Can anyone help steer me in the right direction as far as getting some of these fixed? I know sometimes having move than one code can narrow the options of what the root cause is so I will post all of them:

 

U1000-Class 2 data link malfunction

U1255-Class 2 communication malfunction

 

C0300-Rear Propshaft signal circuit malfunction

C0305-Front propshaft speed sensor system malfunction

C0306-Motor A/B circuit malfunction

C0321-Transfer case lock circuit malfunction

C0327-Encoder circuit

C0359-4LO discrete output circuit malfunction

C0374-General system malfunction

C0379-Front axle circuit malfunction

 

P0141-Oxygen sensor heater circuit bank 1 sensor 2

P0154-Oxygen circuit activity detected bank 2 sensor 1 intermittent

P0155-Oxygen circuit heater circuit bank 2 sensor 1

P0161-Oxygen sensor heater circuit bank 2 sensor 2

 

I think P0141, P0154, P0155, and P0161 just means I need to replace all 4 O2 sensors? or could it mean something else?

 

Also the "service 4wd" and "rear access open" messages on the dash. It seems the truck thinking the rear access is open is why 1:the rear wiper won't work 2: the interior lights will only come on when I push the dash button but not on extt/entry and 3: I can't lock the doors while the truck is on.

 

The U1000, found online it probably DOESN'T mean the PCM is bad, possibly a bad ground, but I also have the U1255, IDK if they are related.

C0300 says it could commonly be four-wheel drive switch or actuator failures.

For C0300 and C0305 I found this page: Chevy bulletin

C0306 youtube-bad ground-I am going to go try and do this tonight if weather permits.

 

 

 

First check your O2 sensor fuses. Then check G103 which is located at the back of the passenger side head.

Here is a Schematic to help you further. Also If the fuse is blown, check all the O2 Sensors for damage.

 

 

[carnau]

On the transfer case problem, Make sure the wires to the transfer case are not rubbing on the Front drive shaft. I have seen that multiple times. If it is just repair the wiring.

If not you will need a encoder motor range sensor which is very easy to replace.

 

Sensor. - http://amzn.to/2FYekmp

[Xtreemjedi]

On 3/20/2018 at 7:51 PM, carnau said:

First check your O2 sensor fuses. Then check G103 which is located at the back of the passenger side head.

Here is a Schematic to help you further. Also If the fuse is blown, check all the O2 Sensors for damage.

 

 

 

Thank you very much I will look into this later this week. I will have to research how to read that schematic. When looking at the O2 sensors for damage, you mean physically from like a rock or something, or would there be damage to the portion inside the exhaust? Also is there 4? 1 for each bank pre and post cat.

[rjgti]

yes and if you can't read that print, you will have a very tough time doing electrical checks