ALDL

[John Hess]

Here we go again.  The ALDL information IS NOT on pins A&B.  A is 
ground.  B is 5-6 volts from the Computer. E and/or M is the serial 
ALDL data.  Shorting A to B only has the effect of causing the Check 
Engine light to flash in a manner that will reveal any trouble codes. 
 The ALDL is a serial bit stream that includes information such as 
spark retardation, Throttle position, Injector duty cycle, Air inlet 
temperature, ad nauseum.  What you say might be true as far as it 
goes;  but, I don't think that it is a response to the question.  I 
use a Diacom  Plus to read the ALDL data.

----------
From:  Daniel Burk[SMTP:ws6transam at voyager.net]
Sent:  Saturday, December 14, 1996 4:04 PM
To:  diy_efi at coulomb.eng.ohio-state.edu
Cc:  wbraden at ryker.itech.cup.edu
Subject:  Re: ALDL

Wade:  Your ALDL information is on pins A & B, which you get by 
shorting
these pins out with a 20 K resistor, a 10 K ohm resistor, or a 3.9 K 
ohm
resistor depending on the type of system you have.  Pin D is where the 
information comes out, in the form of a lamp level voltage (zero to
twelve volts).  Your check engine lamp will oscillate with the digital 
data.

If you use a 20K resistor instead of the 10 K resistor, your car runs 
in
"normal mode" instead of the diagnostics mode, but provides the 20 
byte
data stream anyway.  The 3.9 K resistor puts your car in limp-home 
mode
with a backup spark and fuel control map.


Give that a try.

	-- Dan