DTC Codes on my 02 Tahoe

Discussion in 'Chevy Tahoe Forum (GMC Yukon, Cadillac Escalade)' started by rickp, Nov 19, 2012.

  1. rickp

    rickp New Member

    I ran my AutoCal the other day to look up my error codes and the AC came up with 3 of them.
    P0135, Upstream O2 Sensor (left cylinder bank) heater performance
    P0327 Knock Sensor signal freq outside normal range
    P0332 Knock Sensor signal freq outside normal range

    According to the Haynes manual, the 02 sensor has a feature were it allows the sensor to heat up so it can do its thing. I think that's what wrong with mine. Being that it's the heater performance I dont belive its affecting the air fuel mixture, but I might be wrong about that. Either way I'm planning on replacing them both just to be safe. Anything I should know about doing this?

    My concern is the other 2 codes. I thing my Tahoe has 2 knock sensors. I don't think the engine is knocking or doing anything weird, at least I can't hear anything obvious, so I think the actual sensors are bad.

    So my question is, how difficult is getting to the sensors to replace them. The Haynes manual has me removing the intake manifold, and to be honest I'm a bit intimidated by that. Are there any considerations In should know about if I decide to do this?
    Is there a gasket that needs to be replaced when removing the manifold?

  2. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    The intakes on that year truck are a "dry" intake. There is no coolant running thru it. I would put new intake gaskets in and a new throttle body gasket. I would also buy the harness that connects to the sensors. You should clean the throttle body front and back while it is off. Here is a video, The camera work stinks, and it is not done the best, but it may walk you thru. I have been told that you do not have to pull out the injectors. If you do, I would also replace the o rings on the injectors, but that is just me.
  3. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Most O2 sensors, in use today, have internal heaters, this forces the surface of the sensor to get up to operating temps faster (not having to wait to be heated by the exhaust gases), thus letting the PCM get into "closed loop" earlier.

    If the PCM thinks one of the O2 sensors is not at operating temp, it will not switch from "open loop" to "closed loop"; resulting in an engine that is not operating as efficient as it possibly could. Perhaps, even an engine that may knock from an incorrect air/fuel/spark.

    Pikey has provided the info to get at the knock sensors if you need to. I might try changing the O2 sensors, clearing the codes and see if the knock goes away. If the knock code returns, try a differnt brand of gas. If you still have the code(s), follow @Pikey into the world of changing knock sensors.
  4. rickp

    rickp New Member

    HEy guys, thanks a lot for the info. Much appreciated.

    I went ahead and ordered everyhting I need to repalce the knock sensors and both 02 sensors upstream of the Cat. I also got the knock sensor harness and the TB and IM gaskets.

    I didn't know anything about the injector o rings, so I'll see if i can pick some up at the dealer near my house.

    Again thanks guys, really!
  5. BillD64

    BillD64 Rockstar

    Before jumping into a major job the first thing you should do is check to make sure the O2 sensor wiring and connections are in good shape and it is getting the proper input voltages. Then drive the vehicle to see if the code comes back. If it does then replace the sensor and see if the code goes away. If the sensor code goes away then clear the other codes and see if they come back. Just don't jump into replacing the Knock Sensors right away. If DTCs P0327 and P0332 are set at the same time, inspect for poor connections at the KS harness jumper, located at the left rear side of the intake manifold. That could save you the effort and cost of replacing the sensors. Do the simple stuff before you jump into major repairs. The codes do not tell you what to replace, they tell you where to start the diagnostic process. A lot of engines have been torn apart and parts replaced when all that had to be done was pull the connectors apart and check for corrosion on the connector pins or connector pins that are not making good electrical contact for some other reason. The three images below show the diagnostic procedures from the GM Service Manual for diagnosing the KS codes. P0327-P0322 02 Tahoe1.jpg P0327-P0322 02 Tahoe2.jpg P0327-P0322 02 Tahoe3.jpg

  6. rickp

    rickp New Member

    Hey Bill,
    you know that's a good point. Thanks for this great info. It'll come in handy.

    Let me ask you though, even if the harness is bad, I still have to take the manifold off right? If so, even if the KS are good it might be a good idea to replace them as preventive maint. Its an older truck being an 02. I would hate to have to remove the IM replace the harness just to do it again in the future for the KS, and have to get another gasket for the IM and even possible for the TB.

    Thanks again
  7. VAB

    VAB New Member

    I know this is an old thread buy I'd thought I'd give it a try. I have the P0327 and P0332 codes coming up. I replaced the sensors, harness, checked impedance, etc... I'm thinking the ECM may be to blame. Question: what voltage, if any, should there be on pins 11 and 51 of an ECM that functions correctly? Thanks
  8. BillD64

    BillD64 Rockstar

    Hard to say for sure. The knock sensors are just a microphone tied to ground on one side with the other being input into a transistor inside the PCM. That means it it may be floating at a level that is determined by the circuit network inside the PCM. Figure about +2.5 volts to +3.0 volts. GM's FSM's don't show the internal circuitry so I am just guessing as to the value.


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