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  1. #1
    LTX Member


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    Danno
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    1996 Firebird Formula
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    Default 96 Formula Throwing P0154 Code

    I Picked up a 96 Formula 6-speed for cheap. The car has headers, cam, and ported heads. The downside is that it has issues. I am getting a P0154 code . The P0154 (Oxygen Sensor Bank 2 Sensor 1 No Activity) about has me at my wits end. I replaced both 02 Sensors with NTK ones, since the ones in it were in there for who knows how long.

    After I replaced the sensors, both 02 Sensors were switching like they should on the scan tool. Now I have P0154 back again. The drivers side sensor sits at .2 volts with the Key on Engine Off. The passenger side just reads a steady .445 reference voltage. I pulled up all the wiring for the passenger side sensor. Some one did a home made wire extension by chopping the engine harness and soldering in extra wire.

    The soldering job was not very good, so I redid it. I then tested the wires With the key on I get 12 volts on the pink wire, .8 volts on the tan low signal wire, and 1.5 volts on the Purple High signal wire. I checked the ground wire in the plug and get a resistance of .1 ohms, so the ground is good. I plugged the sensor back in and still only got reference voltage on the scanner.

    I then pulled the PCM and and checked continuity between pins 7 & 8 on the clear connector and the purple and tan wires on the sensor connector. continuity was good with a .4 Ohm resistance on both wires. I plugged the sensor back in, and still only get reference voltage. Could the sensor already be bad? Could it be a PCM issue? Thanks.
    1996 Firebird Formula (A Working Progress )
    2002 Camaro Z/28 M6 (Sold but not Forgotten!)

  2. #2
    LTx Guru


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    1994 Formula
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    Default

    How long did the new NTK sensors work correctly, before you got the code for one of them? To determine if it's a wiring problem or a sensor problem, swap the sensors side-to-side, to see if the code follows the sensor (faulty sensor), or the code stays on the same side (faulty wiring).

    How are you reading the sensor voltage- scanner/scan software? Without the engine running, the voltage will depend on the temp of the sensor. Cold sensors don't produce a voltage, so you will see the ~450mV reference voltage. The sensors should warm up slowly as the heater does its job, but relatively slowly. As the sensor warms up with the engine not running, the voltage is going to drop. Did you check the red heater wire voltage using the black wire as a ground (and not a chassis ground)?

    I believe it’s generally not a good idea to back-probe voltage at the PCM, unless you have a high impedance meter. Otherwise you can damage the PCM.

    94 Formula A3+1: 381ci forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / Comp Cams solid roller / TH400+GearVendors OD / 4.11's/Strange 12-bolt / 300-shot (dry) N2O / Spohn Suspension / 6-pt roll bar /AutoMeter instrumentation / MoTeC M48 Pro engine management system /a few other odds 'n ends.

  3. #3
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    Default

    My meter is a 10 Megaohm input on the DC setting. I'm getting the sensor voltages with a scan tool, and I drove the car for two days around town before I got the code. This morning I plugged the PCM back in and checked the sensors again while KOEO. On the scan tool the driver's side sensor slowly dropped from .440 to .2 as the sensor warmed up. The passenger side did not move off of .445 volts like before. I checked the heater wire voltage using the ground in the sensor connector.

    I then swapped the sensors, and checked again with KOEO. Now both sensors sit at .445 volts and don't move down. I then got under the car, and both sensors were warm/hot to the touch, so the heaters are working. This one has me baffled. Why are both sensors not working correctly? Faulty batch or sensors? I have a set of NTK sensors in my Dodge Charger R/T and they work great.
    Last edited by Seawolf18; 05-13-2019 at 12:38 PM.
    1996 Firebird Formula (A Working Progress )
    2002 Camaro Z/28 M6 (Sold but not Forgotten!)

  4. #4
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    Danno
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    Default

    I swapped the sensors back again, and now the drivers side sensor volts slowly start dropping like before. I think its a combo of two problems, one bad sensor and wiring issue still on the passenger side. I'm going to get a new o2 sensor connector and chop out the home made wire extension back to the factory wires, and get a proper sensor extender wire harness, like the driver's side has. I also ordered some AC Delco AFS75 sensors this time.

    I also noticed a P0336 Crank Position sensor code today as well. I pulled the sensor and found a large crack down the body of the sensor. I guess I will be putting one of those in as well.
    Last edited by Seawolf18; 05-13-2019 at 10:29 PM.
    1996 Firebird Formula (A Working Progress )
    2002 Camaro Z/28 M6 (Sold but not Forgotten!)

  5. #5
    LTx Guru


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    Most people seems to feel the AC Delco sensors perform better.

  6. #6

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    Quote Originally Posted by Injuneer View Post
    Most people seems to feel the AC Delco sensors perform better.

    ^^^ Yup, worked best for me, had O2 issues, then replaced them with AC Delco, trouble gone..

  7. #7
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    Danno
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    I finally got all the add on wiring removed, the O2 sensor connector soldered back on to the factory wiring, and the proper o2 extensions hooked up. Installed the new 02 sensors and tried it out. According to the scan tool they are both working now. The car ran much much better when I started it, and the sensors look to be switching like they should be. Thank you for the help.

    20190517_144037.jpg
    Key on Engine Off.
    1996 Firebird Formula (A Working Progress )
    2002 Camaro Z/28 M6 (Sold but not Forgotten!)

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