Re: 5kt fault codes

[orin@netcom.com (Orin Eman)]

> I am trying to track down the cause of difficult cold starting in my 86 
> 5kt.  The engine will start and run smoothly, but needs to be cranked 
> for a while.  When checking for fault codes in memory, 2312 is the only 
> input diagnosis code to appear.This is supposed to be for the coolant 
> temp sensor.  I have checked this and the blue wire to the ECU, and 
> they seem O.K.  Is the 4-prong thermo switch under the coolant outlet 
> also associated with this code, or am I missing something?  The ECU is 
> a MAC 11B by Hitachi. Do I also need to display the output fault codes? 
> (with engine off)  I am baffled!

OK, I looked it up in the disassembly.  2312 means that the CPU thinks the
sensor is open circuit or short circuited.  (It actually checks the ATOD
converted value - if less than 8 or greater than 0xE4, it generates the error
- normally this converted value is 0x12 to 0x14 on my 86 5kCSQ when the
engine is warm.)  Note that this check is done many times each second,
and the MAC11B will generate the error code if it sees a bad value just
once, so your problem may be intermittant.

Does the fault code appear if you just crank the engine for a few seconds
then dump the input codes?

You may want to run the output tests to see if the cold start injector
works.


Orin.