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Re: Project 4ktq update

Todd Phenneger writes:
> [ KH engine install in 4KQ ]
> 	On the list for this weekend is to get the downpipe in and install
> the CIS system and wiring hooked up.  The under dash wiring is basically
> done except for the light to pull the codes.  (I'm ocnfused on this)  I
> though I just needed to wire the wire into a light socket like the OXS
> light since its disconnected on my car.  Then use the fuse to plug into
> the relay to flash it.  But there has been talk of needing a seperate
> Intermittent switch to do this.  why do i need this???

If you're running the KH engine ECU (MAC-07A) then the code dumping
stuff is very different than the MC engines.  The tachometer and
the "check engine" light are the display for this, and the brake
pedal is the control.

On the KH with MAC-07A:

1. Start engine, run until warm, hopefully with boost.
2. Close both the full throttle and idle switches for at least 3 seconds.
   This sets the ECU into fault memory dump mode.  The tach should read
   7000 at this point and the check engine light should be on.
3. Press brake pedal once.
4. If there are faults, the tach will indicate anywhere between 1000
   and 6000 and the check engine light will be on or off.  You look this
   up in the table below for the fault.  If there is no fault, the tach
   will indicate 7000 and the check engine light will go off.  You can
   switch off ignition to exit the diagnostic mode.
5. Loop back to step 3.

Here is the fault table:

Tach		CE light	Sourc
---------------	---------------	--------------------------------
1000		Off		RPM sensor
1000		On		Knock control
2000		Off		Ignition timing sensor
2000		On		Knock sensor
3000		Off		Hall sensor
3000		On		Intake air temp sensor
4000 or 6000	Off		Vacuum hose from intake manifold to ECU,
				or short circuit in idle switch or wiring,
				idle switch stuck.
4000		On		Coolant temp senser
5000		Off		Pressure sensor in ECU
7000		Off		End of diagnostic sequence
7000		On		Beginning diagnostic sequence

The Bentley manual for the 84+ 5000S/T/TQ has more details about this.

What this all means as far as wiring is that the tachometer on
the KH (and MC) cars are connected to the ECU, as opposed to the
ignition coil as on the 4KQ.  I don't know if the 4KQ tach can be
re-wired to the MAC-07A ECU and read correctly, but you can try.
Also, there is a wire that runs from the MAC-07A to the brake light
switch you need to add to make this all work.

You really do need to study the wiring diagram of both the KH cars
(84/85 5000S turbo) and the 4KQ carefully and make sure you got all
the details worked out.

96 A4 2.8 quattro
84 5000S 2.1 turbo
80 4000 2.0
    ///  Ti Kan                Vorsprung durch Technik
   ///   AMB Research Laboratories, Sunnyvale, CA. USA
  ///    ti@amb.org
 //////  http://metalab.unc.edu/tkan/