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99 z28 lag/stutter please help!!

This is a discussion on 99 z28 lag/stutter please help!! within the General Help forums, part of the LSx Technical Help Section category; Originally Posted by pajeff02 For the front O2 senders, the connectors on the vehicle harness (not the senders) should have ...

  1. #61
    Junior Member clewis05's Avatar
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    Quote Originally Posted by pajeff02 View Post
    For the front O2 senders, the connectors on the vehicle harness (not the senders) should have four (4) wires: Pink, Black, Purple/White and Tan/White on both the driver and passenger side. The Pink and Black wires are the heater circuits for each sender. With the ignition energized, you should have 12 volts on the Pink wires. For the Black wires you should have continuity to ground.

    Next check the senders themselves for a blown heater circuit. Eyeball the male and female side of the connectors to determine which wires on the O2 senders match up to the Pink and Black wires on the vehicle harness. Perform a continuity test on the heater circuit by then probing those two wires on the O2 sender harness (not the vehicle). If the heater circuit is good, you should have continuity. If the heater is blown, you will have an open circuit and no continuity.

    If that tests ok, then let's probe for power to the sensor portion of the senders. With the sensors still unplugged, rig a jumper wire from a good chassis ground to the Tan/White wire (which is the low signal circuit). Hook up your scanner and without starting the vehicle energize the ignition. You should see from 350 mV to 550 mV on your scanner (not your multimeter) for the jumpered sensor. (See Step 4 in the diagnostic chart if you need further explanation of this test).

    Be sure to check both Bank 1 (driver side) and Bank 2 (passenger side) so that you can compare your results. Bank 2 appears to be working correctly, so you should only find an issue on Bank 1. Post up your test results when completed.
    Sorry Jeff, I have been gone for the last month doing training. Never got a chance to get under the car and probe around. Will do it this weekend. If I have any issues ill get on here and let you know what I find out or dont find out haha Hopefully I can figure this damn thing out

  2. #62
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    I know what you mean -- some times takes me a couple of weeks to get around to diagnosing a problem and then fixing it.

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    Junior Member clewis05's Avatar
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    Quote Originally Posted by pajeff02 View Post
    For the front O2 senders, the connectors on the vehicle harness (not the senders) should have four (4) wires: Pink, Black, Purple/White and Tan/White on both the driver and passenger side. The Pink and Black wires are the heater circuits for each sender. With the ignition energized, you should have 12 volts on the Pink wires. For the Black wires you should have continuity to ground.

    Next check the senders themselves for a blown heater circuit. Eyeball the male and female side of the connectors to determine which wires on the O2 senders match up to the Pink and Black wires on the vehicle harness. Perform a continuity test on the heater circuit by then probing those two wires on the O2 sender harness (not the vehicle). If the heater circuit is good, you should have continuity. If the heater is blown, you will have an open circuit and no continuity.

    If that tests ok, then let's probe for power to the sensor portion of the senders. With the sensors still unplugged, rig a jumper wire from a good chassis ground to the Tan/White wire (which is the low signal circuit). Hook up your scanner and without starting the vehicle energize the ignition. You should see from 350 mV to 550 mV on your scanner (not your multimeter) for the jumpered sensor. (See Step 4 in the diagnostic chart if you need further explanation of this test).

    Be sure to check both Bank 1 (driver side) and Bank 2 (passenger side) so that you can compare your results. Bank 2 appears to be working correctly, so you should only find an issue on Bank 1. Post up your test results when completed.
    Ok Jeff. I finally got up under the car today and performed all the tests you listed. Both Pink wires put out 11.8V. Both black wires had continuity to grounds. I performed the continuity test on the heater circuit and both sides passed. I did the jumper wire and took 2 pictures of my scantool. The first pic is the Bank 1 and the other is the Bank 2. Whats the next step I need to do?


    Attachment 25945Attachment 25946

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    I do not see the reading for "O2S11" which would be your driver side front O2 sender -- the one that is giving you fits.

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    Junior Member clewis05's Avatar
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    It's the first line on the picture

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    Whoops. Guess I needed more sleep last night.

    Ok - it shows zero volts still. If you have already swapped the front O2 senders side-to-side, then you almost have to have a connection or wiring issue. The pins in the connectors can bend out of place, corrosion can be an issue, and there have also been problems tracked to the connectors at the PCM. Easiest test would be to identify the pinout at the PCM and then run a continuity test from there to the plug at the sender.

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    Junior Member clewis05's Avatar
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    Hahaha we all have them kinda days. Do you happen to know which of the many pins is the exact one I need?

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    The PCM connectors are red and blue -- you want to remove the blue one which is referred to as "Connector 1". Step one when messing with the PCM is always to disconnect the battery. If I recall, the connector at the O2 sender is labeled "A-B-C-D". Again, we are only messing with your driver side O2 sender, above the catalytic converter (engine side). With your O2 sender unplugged, you want to probe the harness connector for continuity as follows:

    "A" Tan/White wire - this is the low signal wire that travels to Pin 29 on the PCM connector.

    "B" Purple/White wire - this is the high signal wire that travels to Pin 69 on the PCM connector.

    "C" Black wire - this is chassis ground (confirm that you have continuity to ground on this wire).

    "D" Pink wire - this is power to the O2 sender and you should have 12 volts with the key in "run" and battery hooked up.

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    Junior Member clewis05's Avatar
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    Alright thanks Jeff. I'll let you know what I find out

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    Junior Member clewis05's Avatar
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    Quote Originally Posted by pajeff02 View Post
    The PCM connectors are red and blue -- you want to remove the blue one which is referred to as "Connector 1". Step one when messing with the PCM is always to disconnect the battery. If I recall, the connector at the O2 sender is labeled "A-B-C-D". Again, we are only messing with your driver side O2 sender, above the catalytic converter (engine side). With your O2 sender unplugged, you want to probe the harness connector for continuity as follows:

    "A" Tan/White wire - this is the low signal wire that travels to Pin 29 on the PCM connector.

    "B" Purple/White wire - this is the high signal wire that travels to Pin 69 on the PCM connector.

    "C" Black wire - this is chassis ground (confirm that you have continuity to ground on this wire).

    "D" Pink wire - this is power to the O2 sender and you should have 12 volts with the key in "run" and battery hooked up.

    Ok just got done. There is continuity through pin 29 to "A' as well as pin 69 to "B" Ground still is good. And the volts I'm pulling off the pink wire "D" is 11.62V
    Whats my next steps Jeff.

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    Test results look good -- which is a bummer as I was hoping you would find something wrong that could explain your issue.

    I want to verify that you did in fact swap the front O2 sensors from side-to-side and that the problem remained on the driver side?

    I also want to verify that you inspected the harness connection for the front driver side O2 sender and that everything in both the male and female ends appears good?

    Calling for some backup on this one as well...

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    Yea you and me both Jeff. I was hoping that it would of been a break in a wire. Alright I appreciate all the help you giving me man. Let me know what you find out

    -Chris

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    you could also check those wires with a multimeter for a short to ground if you haven't already.
    Last edited by 0rion; 09-29-2014 at 11:20 PM.

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    ^^ Good idea. With the O2 senders unplugged and the PCM connectors unplugged, do a continuity test between the harness connector pins for the low and high signal circuits, heater circuit and the vehicle chassis.

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    The Purple/white wire (O2 high signal, pin 69 to B) must be shorted to ground. Or the PCM is internally shorted to ground on that circuit.

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    Not quite understanding what you're saying Cutlass. Care to elaborate?

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    This picture tells the whole story. The scan tool reads the voltage on the low signal wire. jumper the high and low signal wires together on O211 and it should read .450 volt approximately but it reads 0.000 because the high wire is shorted to ground. IDK. Seems like it has to be.

    With a O2 voltage of 0.000, something somewhere is shorted to ground, somehow. Normally an O2 will never read lower then say .060 volts...

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    Quote Originally Posted by Cutlass View Post
    Click for full size

    This picture tells the whole story. The scan tool reads the voltage on the low signal wire. jumper the high and low signal wires together on O211 and it should read .450 volt approximately but it reads 0.000 because the high wire is shorted to ground. IDK. Seems like it has to be.

    With a O2 voltage of 0.000, something somewhere is shorted to ground, somehow. Normally an O2 will never read lower then say .060 volts...
    I saw that but thought maybe it was because he had a jumper on there somewhere because the next picture there shows .445mv

    I'm still sticking with my original guess that a wire touched a header somewhere.
    Quote Originally Posted by Mean Green Z28 View Post
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    Wire touching a header is the same thing as shorted to ground. So I guess we agree
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    But there is no visible damage done to the wires gents. I already inspected for that. And yes the 2 pics is what it read when I used a jumper wire for the low signal circuit the tan wire. Did that for the driver side and passenger side. Then took a reading of each individually.

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