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Love your C101!!!

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    Love your C101!!!

    I’ve seen a lot of wiring issues with engine swaps, things not working, and things not working correctly, etc.. A lot of that comes down to not knowing or understanding the wire functions that are coming out of c101 and what the e30 is really looking for and what it is giving to the engine harness. So below is a the e30 pin out for c101 and a description of what each pin does and what it should connect to on the engine side. Of course you should always check the ETM for your year and model as well as verifying what you have in your own car before you use any of this information.

    Pin No. – Wire color (for the body side of the connector) – Signal - Description

    Pin#1-Blue - D+ - Wire is connected to the D+ terminal of the alternator then goes through c101 to the cluster. The dash light gets its power from the ignition switch in run or start then to c101 and then to the alt. This pin must be connected at all times or the alternator will not charge the battery after engine start. BMW seems to have standardized the color coding for this signal to always be blue (at least it is in the e30, e36, e46, e39, etc.) In most cases this wire goes straight from the alternator to c101, but in newer models ~2000+ it goes to the DME first and is then passed on to the car.

    Pin#2 – Blue/Violet or Blue/Black – Oil Level (STATIC) – This connection is almost exclusive to the e30. The sole purpose of this is to provide one half of the signal necessary for the Check Control Panel to determine whether or not to illuminate the “Low Oil Level” light. Signal comes from Pin 2 of the 3 pin oil level sensor in the oil pan directly to c101 then on to the Check control panel.. Pin 1 of the oil level sensor is for a ground.

    Pin#3 – No connection

    Pin#4 – Br/Vi – Water temp – This is the signal wire for the e30 clusters water temp gauge. The e30 sensor should be grounded to the engine. The terminal on the sensor should be connected to a wire that connects directly to c101. From there it goes straight to the cluster temp gauge. This sensor is not used by the DME at all. For an accurate temp gauge the correct e30 temp sensor must be used.

    Pin#5 – Black/Brown – Oil Pressure Switch - Wire is connected to the oil pressure switch on the engine where it is grounded. The other end is attached directly to the clusters red oil pressure light. 12v is supplied to the light in the cluster, when the oil pressure dips below 0.4 bar the sensor grounds out, completing the circuit and turning on the light. .) In most cases this wire goes straight from the oil pressure switch to c101, but in newer models ~2000+ it goes to the DME first and is then passed on to the car.

    Pin#6 – Green/Yellow – Fused B+ - This connection is 12V when the ignition switch is in Run or Start position. Power from the battery goes through the ignition switch, is passed through Fuse 9 and then to c101. In the e30 engine harness it is used to power the o2 heater relay, the idle control module, cold start valve, etc.. By the time the m20b25 came in most of these functions were taken up by the DME or not needed and this pin was only used for the o2 relay heater. In a swap this pin should be used anytime a switch 12v, fused supply is needed. For example ECU turn on signal.
    e30sport.net
    '15 Porsche GT3 - 7-speed PDK - Daily Driver
    '86 325es - s54b32tu - 6-speed - Mtech 1
    '89 325is - m20b25 - 5-speed - Individual

    #2
    Pin#7 – Green – B+ - Same as Pin 6 without the fuse. In the e30 this is used by the DME as an off and as a power signal to the coil. In a swap this pin should be used whenever a switched 12v source is needed that is NOT fused. For example ECU turn on signal.

    Pin#8 – Yellow/White – TI – Late models only! found in c104 pin 3 over glovebox in early cars. This is the fuel economy signal from the DME to the cluster. DME outputs a signal that is decoded in the cluster for fuel economy. This signal is displayed in the MPG meter in the cluster then passed on to the OBC. For engine swaps seattlecircuit.com makes a great little converter module that converts the signal for any engine combo.

    Pin#9 – Black – Tach - Late models only! found in c104 pin 1 over glovebox in early cars. This is the engine speed signal from the DME to the cluster. DME outputs a signal that is decoded in the cluster for the tachometer.

    Pin#10 – Violet/Green – Oil Level (DYNAMIC) - This connection is almost exclusive to the e30. The sole purpose of this is to provide one half of the signal necessary for the Check Control Panel to determine whether or not to illuminate the “Low Oil Level” light. Signal comes from Pin 3 of the 3 pin oil level sensor in the oil pan directly to c101 then on to the Check control panel.. Pin 1 of the oil level sensor is for a ground.

    Pin#11 – White/Blue – Service Reset – This wire connect from C101 straight to pin 7 of the diagnostic connector from the gauge cluster. By grounding this it resets the service indicator located in the gauge cluster. This will not work correctly if your SI batteries are on their way out. In e36 engine swaps this function is maintained by connecting to x20 pin 19. For most other engine swaps you are going to have to find another way to ground out this pin conveniently. I have used the OBD port before.

    Pin#12 – Brown/Black – CEL – This is the pin for the check engine light in late cars. 12v is applied to the CEL in the cluster and the wire is then passed through c101 to the DME. The DME grounds the signal if there is a fault and illuminates the light.

    Pin#13 – Violet/Red – Fuel pump – This pin in the power supply for the e30 fuel pump. 12v from the fuel pump relay enters at this pin, passes through fuse11 then heads to the fuel pump in the rear of the car. Obviously you need this one connected.

    Pin#14 – No Connection

    Pin#15 – Black/Green – Unloader relay – Late models only, early had this function combined in pin 18. This is probably the most misunderstood pin in C101. The ground side of the coil of the 2 unloader relays k5 and k7 are attached to this pin. The purpose of this pin is to “unload” the electrical system when the engine is cranking. Meaning that the 2 unloader relays will cut power to unneeded circuits(windows, HVAC, etc.) while the starter is demanding power from the electrical system. This will allow more power to get to the starter since it isn’t being used else where and the car will crank quicker. This pin is connected to terminal 30h on the starter in the e30 and should be connected to terminal 30h of the starter for any swap. Normally when you are sitting with the car off or driving with the engine already on k5 and k7 are grounded to 30h through the windings of the starter motor, to the block and then back to the chases. When grounded the relays are active and you can use all your accessories. During cranking terminal 30h switches to positive once power is applied to the starter from pin 18 in c101. With 30h positive k5 and k7 deactivate and some of your accessories turn off until you turn the key back to the run position. If this pin is not hooked up to anything post swap your windows, HVAC and various other accessories wont work. At the very least this pin needs to be grounded but it should be connected to starter terminal 30h.
    e30sport.net
    '15 Porsche GT3 - 7-speed PDK - Daily Driver
    '86 325es - s54b32tu - 6-speed - Mtech 1
    '89 325is - m20b25 - 5-speed - Individual

    Comment


      #3
      Pin#16 – White/Black – SRS – This is a connection from the SRS airbag system to the diagnostic connection. You don’t need it. It most cases it isn’t hooked up to anything anyway.

      Pin#17 - No Connection

      Pin#18 – Black/Yellow – START – From the start position of the ignition switch to c101 then on to terminal 50 in the starter. This is the signal that tells the car to engage the starter motor and turn the car on. Powered only when the key is in start mode. In early cars the functions of c101 pin 15(see above) were combined into this pin. Instead of the unloader relays being grounded right at the starter they were grounded at the starter through this pin. i.e. the unloaders relays were connected to the start signal before c101 in the car instead of inside the starter. Obviously you need to hook this one up.

      Pin#19 – Brown/Yellow – Oil Temp – M3 ONLY. This is where the M3 cluster sets the info for oil temp. Passes from cluster to c101 then to the e30 M3 temp sensor where it is grounded.

      Pin#20 - - ABS power – In some late model cars the ABS system gets its turn on signal from the Main relay. This connects from the Main relay to c101 then to the ABS module. Without this hooked up you will have no ABS.
      e30sport.net
      '15 Porsche GT3 - 7-speed PDK - Daily Driver
      '86 325es - s54b32tu - 6-speed - Mtech 1
      '89 325is - m20b25 - 5-speed - Individual

      Comment


        #4
        Very nice, thanks!

        Comment


          #5
          i likey would have been nice wiring my c101 but good resource non the less
          "God created turbo lag to give V8's a chance" Taylor D.

          Comment


            #6
            Dude.

            Closing SOON!
            "LAST CHANCE FOR G.A.S." DEAL IS ON NOW

            Luke AT germanaudiospecialties DOT com or text 425-761-6450, or for quickest answers, call me at the shop 360-669-0398

            Thanks for 10 years of fun!

            Comment


              #7
              thanks for that information!

              Re pin 6 and 7; my wiring diagram says that 6 is for the oxygen sensor and 7 is for the ignition. are you saying that 6 is actually the ignition too then? and i can leave 7 unconnected, or connected to anything i want to?

              I need to power my EWS off the ignition, and if this works then its going to save me the headache of running another wire from the ignition. Alternatively, think its sweet to splice the power supply into pin 6 or 7 (7 with an independant fuse)?

              Comment


                #8
                BRAVO. I didn't have any trouble with my C101, but this is amazing. A huge thumbs up to you sir, this definitely needs a sticky.

                You should probably note, though, that this is for late models. Early-early models had the square C101 and my '87 had about half the signals going through the C101, the tach and road speed coming from the C104.
                Last edited by Wh33lhop; 02-26-2010, 12:41 PM.
                paint sucks

                Comment


                  #9
                  Originally posted by Wh33lhop View Post

                  You should probably note, though, that this is for late models. Early-early models had the square C101 and my '87 had about half the signals going through the C101, the tach and road speed coming from the C104.
                  I think for most of the pins that wouldnt be on the early cars i specifed late only or c104 location. nad yes this is only the round c101.

                  ethrty... both 6 and 7 are +12v when the car is in run or start. the ECU power usually comes from the battery(junction block on the firewall on the passenger side) and the on signal would be either 6 or 7 depending if you needed it fused or not
                  e30sport.net
                  '15 Porsche GT3 - 7-speed PDK - Daily Driver
                  '86 325es - s54b32tu - 6-speed - Mtech 1
                  '89 325is - m20b25 - 5-speed - Individual

                  Comment


                    #10
                    Noice! Looks like you've spent some time in the manuals.

                    Originally posted by Roysneon
                    $5 shipped?
                    Originally posted by MarkD
                    You are a strange dude, I'n not answering any more posts from you.

                    Comment


                      #11
                      Sticky
                      "If the sky were to fall tomorrow, the tall would die first."

                      -Dr. Paul Forrester



                      Do I LOOK like I need a psychological evaluation???

                      Comment


                        #12
                        2nd

                        Originally posted by Roysneon
                        $5 shipped?
                        Originally posted by MarkD
                        You are a strange dude, I'n not answering any more posts from you.

                        Comment


                          #13
                          thank you so much for this!!! :D

                          91 318i | 87 535iS

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                            #14
                            awesomeness!
                            I got a fender roller now! LMK if you need me to roll your fenders or want to rent the tool from me locally.

                            Paypal: vdang5@gmail.com

                            Delta Auto Care
                            2875-C Towerview Road
                            Herndon, VA
                            703.435.1375

                            My Feedback Thread: Evil_Twin

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                              #15
                              Originally posted by Wh33lhop View Post
                              BRAVO. I didn't have any trouble with my C101, but this is amazing. A huge thumbs up to you sir, this definitely needs a sticky.

                              You should probably note, though, that this is for late models. Early-early models had the square C101 and my '87 had about half the signals going through the C101, the tach and road speed coming from the C104.
                              Mine too.
                              1987 BMW 325is | Frankenmotor S50 | Supersprint Replica Headers | K&N Intake | Gutted Stock Midpipe | Zimmermann Rotors | Stainless Brake Lines | Porterfield Racing Pads

                              Comment

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