As mentioned in the title, I have a PFC for a FC3S, not a FD PFC rewired for FC3S use.

In order to get the check engine light I followed the instructions from http://www.clubrx.org/media/pfc/pfcwarn.pdf. The wire that was originally in 1E (check engine light) is now connected to the 1V pin on the powerFC. The check engine light is now on, but it won't turn off even when the car is running.

Is this configuration correct? Do any other FC3s guys have the PFC running correctly? Dale any ideas?

 

Dale's instructions are for FDs which do work.
Thus for your FC, you have to work it out.

 

I don't have an s5 T2 (I have an s4) but I'll just throw out some ideas for you.

First, in your datalogit do you have knock warning and all those other warnings that trigger the CEL enabled? Turn them all off and see if that turns off your CEL. Make sure that it isn't a configuration issue in the power FC somehow.

You need to figure out if the FD and the FC trigger the check engine light in the same way. If you read page Z34, Z38 of the s5 FSM ("Turbo engine control" subsection in the s5 wiring diagram portion of the FSM floating around in the 2nd gen FAQ) it says that a 12V signal TURNS OFF the CEL, either directly or somehow through a relay (but there doesn't seem to be a relay from what I can see). Under 5 volts keeps it on. This is with some kind of check connector grounded, but I'm not sure if that even affects it. So you need to figure out:

1. What voltage is coming out of FD pin 1V when the CEL is actually supposed to be on, and what is coming out of that pin when it is off? Set your knock or duty cycle threshold really low in the datalogit so it would hopefully trigger the CEL all the time for purposes of this diagnosis. I suspect that FD pin 1V is simply putting out no voltage during normal driving, so your CEL stays on because it is expecting 12V under normal conditions.

2. Figure out how to get the < 5V to your CEL in the idiot cluster when you are trying to trigger it, and how to make sure it usually has 12V normally so it doesn't stay on all the time. I'm not a real wiring guru yet so I can't tell you what combination of resistors/relays/switches/whatever would do that, but does the concept make sense? This assumes that I am interpreting the diagrams correctly. Double check what I'm saying and see if it makes sense to you.

If you read page T-44 in the s5 FSM ("body electrical systems") it has a circuit diagram of the idiot cluster if that is of any use.


I would be interested in what you find out. I may try and wire up an LED on my instrument cluster to flash because the s4 has no check engine light.

 

It actually seems that the CEL is being triggered correctly. However instead of turning on to indicate an error, it is turning off.

Looking at the wiring for the indicator, it is supplied 12V from the battery and the factory ecu or whatever was switching on a ground to complete the circuit. Maybe the powerFC switches off a ground and is normally closed.... hmmm

I think that means I'll have to put a relay activated by the PFC to turn on the CEL circuit.

I'll give it a shot this weekend.

 

Got it to work... SPDT relay and a little backwards thinking!!! If you want a little more info, lemme know and i'll see what I can put up as documentation

 

yes I would like a quick rundown if you don't mind. I have an s4, which doesn't have a CEL, but I would like to perhaps put the CEL output to an LED that I can mount near my instrument cluster.

 

Here we go! I took a couple days, but figured it out. I’m going to include all the details that I picked up along the way so you have even more understanding.

Initially, I read the instructions from http://www.clubrx.org/media/pfc/pfcwarn.pdf which states that PIN 1V on the powerFC is the output for the check engine light. The first thing I needed was to find what pin 1V did on the S5 harness… after inspection of the PFC harness I found that it doesn’t route a wire from the S5 pin 1V into the PFC pin 1V. I personally didn’t want to take apart the PFC harness, so I approached with the following thoughts “Is there anything on the S5 connector #1 that I don’t need?” After reviewing the pinout, I landed on pin 1P, the heat hazard sensor. I pulled pin 1P from the S5 connector and made it hang free!!!! I then replaced it with pin 1E which happens to be the ….. CHECK ENGINE LIGHT! Perfect… no wait! I need to make sure that gets to PIN 1V on the PFC. The S5 Pin 1V runs to on PFC pin 2I. I removed it from 2I and connected it to 1V. Voila! Check engine light is on!





It’s on all the time… in fact, it gets turned off to indicate a malfunction. WHY? After testing voltages and such here is what I found. The battery runs 12V to the CEL (check engine light) and then needs a ground. PIN 1V on the PFC supplies that ground, but as an indicator that everything is ok. The ground is interrupted (no signal, open circuit) when things go wrong. How the hell do you use “no signal” to make something work? A relay!!! A SPDT relay. Here’s how it works for those that don’t know. There is a 12v source run through a coil when it is grounded (current running through it), the coil generates a magnetic field which basically throws a switch. In this relay the switch is between 2 circuits. When there are two circuits, there are two states for each circuit. ON or OFF. When one is ON, the other is OFF. One of these circuits will be open when the magnetic field is turned on. Since, the ecu ground is on all the time and I want the CEL off until the field is off, I need to use the circuit that is “normally closed “(the circuit is active when the magnetic field is off).





Here’s what I bought:
12V relay only 37.5ma draw. This means that just a tiny bit of current is running into the ecu at pin 1V.
http://www.radioshack.com/product/in...entPage=search

Circuit board with metallic points I can solder on. You can cut it to size.
http://www.radioshack.com/product/in...entPage=search

Wire, solder, soldering iron (low wattage!!) My 60w iron melted the points off the board.

I didn’t think to take pictures as I was working on it so you won’t see the process however I need to do this again for a friends car, so I’ll document it that time with video.

Take a look at the diagram.


I’ll try to answer more questions, but I’m tired now.

Feel free to ask more questions. I'd also recommend downloading the images just in case you think you may need them. My web server may not be up forever.

 

If I'm going to wire this up for an LED, I would use the SPDT relay to switch +12V when the ground signal is interrupted from the PFC, and use that as a power source for the LED. Correct?

I have the Banzai Racing s4 kit so I don't have a CEL. I have to look on the harness and see if there is even a wire coming from PFC pin 2I.

 

You would need to tap into pin 1V on the PFC, there is no wire installed in the connector for that pin.

 

There are two circuits here.

Circuit A:
You'll hook up the 12V on either side of the normally closed circuit, it doesn't matter. And yes your LED will be in that normally closed circuit. It gets switched on and off by the relay.

Circuit B:
The wire for PIN 1V will be cut. The ecu side of the wire will connect to one side of the coil on the relay. The harness side of that same wire will tap into a 12V source that turns on with ignition, I used pin 1B.

 

Good stuff! Glad you figured it out!

Dale

 

reminder bump

 

lol

did exactly the same and found out exactly the same as you did.. i also just moved the 1P pin on the AP Engineering harness to the 1V pin.. now it seems I will have to installed a relay of some sort to invert the singal.

small question: is the pin at 1v pulled to 12v when the cel should be on, or is it just stopped from being pulled to ground?

 

updated link

http://www.xsadclan.com/files/PFC/pfcwarn.pdf