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Which pins for the O2 sensors at the PCM? (OBDII) **AN EXAMPLE THREAD**

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  • Which pins for the O2 sensors at the PCM? (OBDII) **AN EXAMPLE THREAD**

    Note to other members: this thread is the perfect example of the proper progression of a trouble-shooting thread!
    KevinD


    Ughhh...I despise OBD2. The car is a '96 PGT, CA emissions, 5-sp, unmodified.

    Anyway, I'm trying to locate a problem with a P0154 code (O2 seonsor CKT no activity, Bank 2 Sensor 1). I'm assuming that is the upper sensor on the rear bank. So either the sensor is not working, or it is working and I have a bad wire/connection between it and the PCM. So here be the questions:

    *on the 96, the 3-wire sensors are the uppers and 4-wire lowers, correct? As in, before the pre-cats 3-wire, after the precats 4-wire?

    *How do you test the 3-wire sensor with a multimeter to determine if it's functioning correctly? I believe with the 4-wire you probe the 2 gold pins while idling and get the 0.3-0.7V oscillation. The 3-wire only have one gold pin.

    *At the PCM, which wires should be tested for the sensors? Connector C247 has 4 heated O2 sensor pins (3, 4, 18, 19), and connector C248 has 2 more (2, 3) which makes 6 total. Which are the right 4? And what is 'left' and 'right'? The diagram has weird lingo (right rear, left rear, right front, left front)...



    This car is kicking my ass !
    Last edited by KevinD; January 20, 2007, 02:37 PM.
    90 Mazda 323 - KLZE, fender-flared, right hand drive, 2350 lb fully loaded sex machine. || Pic Thread ||- SOLD
    93 PGT FRANKENPROBE - 10.24 @ 139.9 mph ||545 whp @ 20 psi || Timeslip || Dyno slip|| Build Thread - GONE
    97 GTS - Rear Wheel Drive KLZE, 6-speed, 3.90 Torsen LSD, 2650 lb, daily driver! - Build Thread - GONE
    90 Ghettocet KLiata - forever WIP

  • #2
    It's the upper sensor on the front bank...
    Try looking here.
    The 3-wire sensors use a common +12V, with a sensor wire and a heater wire running back to the PCM. The connections on C248 are the heater connections; the sensor outputs all go to C247.
    KevinD
    Last edited by KevinD; January 1, 2007, 10:43 PM.
    1995 Sapphire Blue Mustang GT Convertible, 2006 Storm Red Metallic Mercedes-Benz CLK 350 Cabriolet, 2006 Dark Shadow Gray Ford F250 V10 Supercab 4x4, 2004 Perlite Gray Metallic Mercedes-Benz E320 4Matic, 2002 Burgundy Pearl Suzuki XL-7 Touring, 1971 Spring Green Jeep J4000 Gladiator, 1966 Signal Flare Red Ford Fairlane, to name a few...

    Comment


    • #3
      Bank 2 sensor 1 is the front bank, top O2 sensor. The Bank 1 sensor is always on the bank with the #1 cylinder.

      1) Yes

      2) You test it the same way. The 4th wire on the 4-wire O2 sensors is a ground for the O2 sensor that usually goes back to the PCM. It is a redundant ground. On a 3-wire O2 sensor, the sensor grounds through its case, to the exhaust manifold/pipe. So, put the positive probe of your DMM on the O2 sensor pin, the negative to any good ground.

      3) Let me check on this for you.
      EDIT: OK, found it. The O2 sensor you are looking at is the Left Front O2 sensor. The pin you want is Pin 3 on C248, and should be a pink wire.

      Good luck!
      Last edited by ouch1011; January 1, 2007, 10:49 PM.
      Kevin B - Former Probe-owner
      06 Legacy GT
      98 Legacy GT

      Comment


      • #4
        Originally posted by ouch1011
        The pin you want is Pin 3 on C248, and should be a pink wire.
        Are you sure about that? The sensor output wires are the shielded leads, and they all run to C247...

        KevinD
        1995 Sapphire Blue Mustang GT Convertible, 2006 Storm Red Metallic Mercedes-Benz CLK 350 Cabriolet, 2006 Dark Shadow Gray Ford F250 V10 Supercab 4x4, 2004 Perlite Gray Metallic Mercedes-Benz E320 4Matic, 2002 Burgundy Pearl Suzuki XL-7 Touring, 1971 Spring Green Jeep J4000 Gladiator, 1966 Signal Flare Red Ford Fairlane, to name a few...

        Comment


        • #5
          Man, I'ma have to do a lot of probing if the sensor checks out ok!
          90 Mazda 323 - KLZE, fender-flared, right hand drive, 2350 lb fully loaded sex machine. || Pic Thread ||- SOLD
          93 PGT FRANKENPROBE - 10.24 @ 139.9 mph ||545 whp @ 20 psi || Timeslip || Dyno slip|| Build Thread - GONE
          97 GTS - Rear Wheel Drive KLZE, 6-speed, 3.90 Torsen LSD, 2650 lb, daily driver! - Build Thread - GONE
          90 Ghettocet KLiata - forever WIP

          Comment


          • #6
            Originally posted by KevinD
            Are you sure about that? The sensor output wires are the shielded leads, and they all run to C247...

            KevinD
            D'oH! You are right. Its the green wire, pin 4, C247.
            Kevin B - Former Probe-owner
            06 Legacy GT
            98 Legacy GT

            Comment


            • #7
              Thanks KevinD and KevinB

              For this year's MSD (which I AM attending), I will tow a big-ol Xerox 1985-vintage copier so I can copy KevinB's '96 shop manual, because I'm sure I won't be done with this car till then
              90 Mazda 323 - KLZE, fender-flared, right hand drive, 2350 lb fully loaded sex machine. || Pic Thread ||- SOLD
              93 PGT FRANKENPROBE - 10.24 @ 139.9 mph ||545 whp @ 20 psi || Timeslip || Dyno slip|| Build Thread - GONE
              97 GTS - Rear Wheel Drive KLZE, 6-speed, 3.90 Torsen LSD, 2650 lb, daily driver! - Build Thread - GONE
              90 Ghettocet KLiata - forever WIP

              Comment


              • #8
                Psst...
                Dan,
                Check this out...

                KevinD
                1995 Sapphire Blue Mustang GT Convertible, 2006 Storm Red Metallic Mercedes-Benz CLK 350 Cabriolet, 2006 Dark Shadow Gray Ford F250 V10 Supercab 4x4, 2004 Perlite Gray Metallic Mercedes-Benz E320 4Matic, 2002 Burgundy Pearl Suzuki XL-7 Touring, 1971 Spring Green Jeep J4000 Gladiator, 1966 Signal Flare Red Ford Fairlane, to name a few...

                Comment


                • #9
                  Originally posted by ouch1011
                  Bank 2 sensor 1 is the front bank, top O2 sensor. The Bank 1 sensor is always on the bank with the #1 cylinder.


                  Now I am thoroughly confused. After initially thinking the opposite, Kevin's explanation made sense.

                  Upon seeing the Autozone diagram, it appears the OTHER way is correct - bank 1 is the LEFT bank (in our case front), and bank 2 is RIGHT bank (our case rear).

                  I tested the front bank top sensor and it triggers fine. Code 154 (bank2 sensor1 no activity) persists. The sensor is not replaceable without removing the darling rear manifold (major cross threadage). I'll test the rear top sensor in a few minutes.

                  Another problem I had was lack of a thermostat, which led to the 1500 rpm idle most of the time, but when hot it idles at 700. Yesterday night on the freeway, the engine temp dropped all the way to the 'C' at the bottom of the gauge! This was with the cruise set at 70mph and no interior heat (not that it was producing any when I tried the HVAC). So I'll add a t-stat also.

                  wtf, mate?
                  90 Mazda 323 - KLZE, fender-flared, right hand drive, 2350 lb fully loaded sex machine. || Pic Thread ||- SOLD
                  93 PGT FRANKENPROBE - 10.24 @ 139.9 mph ||545 whp @ 20 psi || Timeslip || Dyno slip|| Build Thread - GONE
                  97 GTS - Rear Wheel Drive KLZE, 6-speed, 3.90 Torsen LSD, 2650 lb, daily driver! - Build Thread - GONE
                  90 Ghettocet KLiata - forever WIP

                  Comment


                  • #10
                    Check out this site:
                    http://www.asashop.org/autoinc/june2002/techtips.cfm

                    Cliff-notes are that bank 1 is always the bank with the #1 cylinder, which is the REAR bank for us. That is what is standardized by SAE/OBD regulations. They did this in the hopes of clearing up confusion, but it hasn't helped at all

                    And my shop manual is all on CD, from the site listed above. So, you can leave the Xerox at home
                    Last edited by ouch1011; January 8, 2007, 07:58 PM.
                    Kevin B - Former Probe-owner
                    06 Legacy GT
                    98 Legacy GT

                    Comment


                    • #11
                      Ok - the KevinB version is the correct one - Bank1=rear, and Bank2=front on the KL engines.

                      Problems are solved so I'll post the details in case peeps search in the future.

                      Car passed smog after the O2 sensor problem was taken care of, the thermostat was replaced, and 100+ miles of driving to burn off the excess hydrocarbons from the cat.

                      The O2 sensor problem was traced down to the connector - the signal wire had its pin slid out of the connector on the back side - it was a small movement (about 1/8") but enough to break continuity.

                      The high HC were resulting directly from running pig-rich.

                      A secondary problem was that the cat never reached operating temps due to the thermostat being stuck open, which kept the engine cool at all times. Once I replaced it, the cat was working fine.

                      Interesting side note - the KFZE (2.0L V6) uses the same thermostat as the FS (U.S. 2.0L 4-cyl) motor. The DE t-stat is too small in diameter and won't fit.

                      I couldn't have done it without the scan tool - not bad for a free Autozone rental. Now to get my deposit back

                      Thanks Kevins for yer help!
                      90 Mazda 323 - KLZE, fender-flared, right hand drive, 2350 lb fully loaded sex machine. || Pic Thread ||- SOLD
                      93 PGT FRANKENPROBE - 10.24 @ 139.9 mph ||545 whp @ 20 psi || Timeslip || Dyno slip|| Build Thread - GONE
                      97 GTS - Rear Wheel Drive KLZE, 6-speed, 3.90 Torsen LSD, 2650 lb, daily driver! - Build Thread - GONE
                      90 Ghettocet KLiata - forever WIP

                      Comment


                      • #12
                        Good find
                        And you're welcome.

                        Note to other members: this thread is the perfect example of the proper progression of a trouble-shooting thread!
                        KevinD
                        Last edited by KevinD; January 12, 2007, 10:00 PM.
                        1995 Sapphire Blue Mustang GT Convertible, 2006 Storm Red Metallic Mercedes-Benz CLK 350 Cabriolet, 2006 Dark Shadow Gray Ford F250 V10 Supercab 4x4, 2004 Perlite Gray Metallic Mercedes-Benz E320 4Matic, 2002 Burgundy Pearl Suzuki XL-7 Touring, 1971 Spring Green Jeep J4000 Gladiator, 1966 Signal Flare Red Ford Fairlane, to name a few...

                        Comment

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