problem on 6.0L vortec

Discussion in 'GM Powertrain' started by marvonh, Jul 10, 2011.

  1. marvonh

    marvonh New Member

    I have a ping on acceleration that gets more pronounced with higher ambient temperature. I have a 6.0l vortec, in a 1500HD Sierra Crew cab. I have replaced all 4 O2 sensors, MAP, TPS, knock sensor, intake gasket, air temp sensor, & MAF. It has 109,000 miles.automatic, & has 3.73 rear gears. I get a P0140 and P0160 codes after taking it down the road at 45-50 miles per hour. If I only use about 1/4 throttle it doesn't ping unless it's above a 100 degrees outside. (It IS Arizona after all). Help!!!

    ---------- Post added at 04:01 AM ---------- Previous post was at 03:18 AM ----------

    I almost forgot, sometimes it "stumbles" when I pull away from a stop.
  2. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Welcome to the club. What year is your truck? Has this problem just started?
  3. marvonh

    marvonh New Member

    No it has been going on for 2 years or so. I have replaced just about all the sensors except for the crankshaft and cam sensors. My truck is a 2001 1500HD Crew Cab Sierra.

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    Here is Information Regarding both Trouble Codes the P0140 and the P0160,

    P0140 - 02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)

    What does that mean?
    The Powertrain control module (PCM) will provide a .45 volt reference voltage to the Oxygen sensor. When the O2 sensor reaches operating temperature, it will generate a voltage that will vary depending on the oxygen content of the exhaust. Lean exhaust generates a low voltage (less than .45V) and rich exhaust generates a high voltage (greater than .45V). O2 sensors on a specific bank marked as "sensor 2" (as this one is) are used to monitor emissions. A Three-Way Catalyst (TWC) system (catalytic converter) is used to control tailpipe emissions. The PCM uses the signal received from Oxygen sensor 2 (#2 indicates aft of catalytic converter, #1 indicates pre-converter) to read efficiency of TWC. Normally this sensor will switch between high and low voltage at a noticeably slower rate than the front sensor. This is normal. If the signal received from rear (#2) O2 sensor indicates that the voltage has "stuck" between .425V to .474 V, the PCM determines this sensor is inactive and this code will set.

    Potential Symptoms
    Your check engine light(CEL), or malfuction indicator lamp (MIL) will be illuminated. There will not likely be any noticeable drivability problems other than the MIL. The reason is this: The rear or post catalytic converter Oxygen sensor does not affect fuel deliver(this is an exception on Chryslers). It only MONITORS the efficiency of the catalytic converter. For this reason, you will likely not notice any engine trouble.

    The causes for a P0140 code are fairly few. They could be any of the following:

    • Shorted heater circuit in O2 sensor. (Usually requires replacement of heater circuit fuse in fuse block also)
    • Shorted signal circuit in O2 sensor
    • Melting of harness connector or wiring due to contact with exhaust system
    • Water intrusion in harness connector or PCM connector
    • Bad PCM
    Possible Solutions,
    This is a fairly specific problem and shouldn't be too difficult to diagnose.
    First, start engine and warm up. Using a scan tool, watch the Bank 1, sensor 2, 02 sensor voltage. Normally the voltage should switch slowly above and below .45 volts. If it does, the problem is likely intermittent. You'll have to wait for the problem to surface before you can accurately diagnose.
    However, if it doesn't switch, or is stuck then perform the following: 2. Shut off vehicle. Visually check the Bank1,2 harness connector for melting or chafing of the harness or the connector. Repair or replace as needed 3. Turn ignition on, but engine off. Disconnect the O2 sensor connector and check for 12Volts at the Heater Circuit supply and for proper ground on the heater circuit ground circuit. a. If 12V heater supply is missing, check the proper fuses for an open in the circuit. If heater circuit fuse is blown, then suspect a bad heater in the 02 sensor causing a blown heater circuit fuse. Replace sensor and fuse and recheck. b. If ground is missing, trace the circuit and clean or repair ground circuit. 4. Next, with connector still unplugged, check for 5 Volts on the reference circuit. If this is missing, check for 5 Volts at the PCM connector. If 5 Volts is present at the PCM connector but not at the o2 sensor harness connector, then there is an open or short in the reference wire supply between the PCM and the o2 sensor connector. However, if there is no 5 Volts present at the PCM connector, the PCM is likely at fault due to internal short. Replace PCM. ** (NOTE: on Chrysler models, a common problem is the 5Volt reference circuit can be shorted out by any sensor on the car that uses a 5 Volt reference. Simply unplug each sensor one at a time until the 5 Volts reappears. The last sensor you unplugged is the shorted sensor. Replacing it should fix the 5 Volt reference short.) 5. If all the voltages and grounds are present, then replace the Bank 1,2 O2 sensor and re-test.

    P0160 O2 Sensor Circuit No Activity......02 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)
    What does that mean?
    This code is for a post-catalyst oxygen sensor that isn't operating porperly or not at all. The catalyst, or catalytic converter is used to control emissions. This particular 02 sensor on Bank 2, position 2 is after the converter on bank 2 and monitors the catalyst efficiency of the catalytic converter on that bank. The PCM (Powertrain Control Module) compares the post-cat o2 sensor to the pre-cat 02 sensors to measure the cat's efficiency. The 02 sensor is a four wire sensor. The PCM supplies a reference voltage to the sensor of about half a volt and also supplies a sensor ground. 12 volts are supplied for the heater element and also a ground for the heater element (the heater in the sensor helps the sensor to warm up faster which allows the engine to reach closed loop sooner).
    The sensor varies the reference voltage the PCM gives it based on oxygen content of the exhaust. The change in oxygen content causes resistance changes in the sensor which affects the 0.5 volt reference voltage. Oxygen sensors are capable of varying the supplied voltage between 0.1 volts to 0.9 volts. Lean exhaust produces low voltage and causes the supplied 0.5 volts to drop. Rich exhaust produces high voltage and causes the supplied 0.5 voltage to increase. Pre-catalyst (front) o2 sensors switch between low and high voltage rapidly one or two times per second.
    However this sensor is a post-cat o2 sensor and may switch much slower & not vary as much (this is normal). If the sensor "sticks" or there are too few switches in a given time period, P0160 may set.

    Symptoms....of a P0160 DTC may include:

    • MIL (Malfunction Indicator Lamp) on
    • May idle or drive poorly
    • Fuel economy may decrease
    Potential causes of an P0160 code include:

    • Holes in exhaust near post cat 02 sensor
    • Bad Bank 2, position 2, o2 sensor
    • Wiring problem, melted harness, broken connectors, etc.
    • Bad PCM
    Possible Solutions,
    It's always best to do a visual inspection of the exhaust system first. Look for holes near 02 sensors or wiring harnesses coming in contact with exhaust components. Repair as necessary.
    1. Start the engine and allow it to reach operating temperature. Using a scan tool, observe the Bank 2 position 2 o2 sensor. If it isn't moving at all this doesn't necessarily mean that anythings wrong. Post cat o2 sensors often switch very little. Increase the engine RPM to a fast idle and then recheck the sensor voltage reading. If it starts switching now, the sensor may be sluggish and/or intermittently going "dormant". Replacing the sensor at this point would be a good idea. Visually check the 02 sensor for contaminates, etc. If you suspect it's contaminated with coolant or oil, replace it. But, if it still isn't responding after increasing engine RPM, turn off the engine and unplug the 2/2 02 sensor. With KOEO (key on engine off) check that there is 12 Volts battery voltage and a good ground to the 02 sensor heater element. If the heater element has no battery voltage it can cause the 02 sensor to be sluggish and not switch properly which can cause a P0160.
    So, diagnose that problem first(there will usually be other codes present). If there is power and ground to the heater element check that the sensor ground is present. If it is, connect a jumper wire between the sensor ground and signal wire. Now the 2/2 02 sensor reading should be low. If so, replace the Bank 2 position 2 02 sensor. If, after connecting the jumper wire, the 02 sensor reading still remains "stuck", check for wiring problems, harness contacting exhaust components, or broken connectors. Repair as necessary. Then recheck. If you can find no wiring problems and the 02 sensor reading on the scan tool doesn't change after installing the jumper wire, recheck at the PCM connector. It may be necessary to clip the signal wire near the PCM in a location that will be easy to repair. If it now shows a low voltage reading, then you know beyond a doubt that there is a wiring problem. At this point clipping the offending wire out of the harness and running a new one may be your best bet. But If it still shows no change, the PCM may be at fault.

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