I have a 1999 Chevy Suburban K1500 5.7L with 173000 miles. I just replaced the starter & ignition switch. Got it running again, but am now showing a check engine light. On a couple of starts since installing the ignition switch the security light has also come on and stayed on, but it didn't affect the drivability. The truck hasn't been driven in the past 3 years and I can't remember if the check engine light was on or not before I stopped using it. I took it to AutoZone and had them pull the codes for it, but they couldn't tell me much beyond that. I also took it to the dealer and they wouldn't tell me anything except "$92 for an emissions diognostic", even though I had the codes in my hand. The codes that came up are as follows:

P0135 - HO2S 11 Heater Condition (Heated Oxygen Sensor Bank 1 Sensor 1)

P0155 - HO2S 21 Heater Condition (Heated Oxygen Sensor Bank 2 Sensor 1)

P0141 - HO2S 12 Heater Condition (Heated Oxygen Sensor Bank 1 Sensor 2)

P0161 - HO2S 22 Heater Condition (Heated Oxygen Sensor Bank 2 Sensor 2)

What is most likely to cause this problem?
-Bad O2 Sensors?
-Bad Cat?
-Electrical/PCM Problems?

Just wondering where I should start and how to test? Thanks in advance for your time.

Do you
have the same problem?
Wednesday, September 12th, 2007 AT 3:15 PM

1 Reply


It is highly unlikely that all four sensors are bad. It is more likely that the fuse is blown. There is a 20amp fuse in the under hood fuse box. It is located along the drivers side fender aft in the underhood area. It should be labeled something like "Eng 1" If thats not blown, Check the grounding point on the lower front right side of the motor next to the harmonic balancer. There sould be a black battery type cable there. Those are the only two item that affect all 4 sensors other than the VCM- vehicle control module itself, but if that was failed, you would probably have other problems too

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Thursday, September 3rd, 2009 AT 9:35 AM

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