rickb@tekig4.UUCP (Rick Bensene) (08/22/85)
Greetings to all: I recently purchased an '85 Chevrolet Z/28, with the Tuned Port Injected 305 V8. This motor is the same as used in the IROC Z/28, and the H.O Pontiac Trans Am. My question is this: Does anyone know anything about the electronic engine controls on this engine? There's the ubiquitous 'CHECK ENGINE' idiot light - a definite indication that GM's "Computer Command Control" is keeping a watch on the engine. I know that Chrysler's Electronic Engine Controls on the 2.2L FI/TURBO engines have a way of 'dumping' the 'fault codes' stored in the computer, (Previous car was a Dodge Daytona Turbo, and I used the feature all the time to aid in diagnosing problems) and am wondering if such is possible on GM's system? Anyone got any information on this? I'll summarize to the net if response is sufficient to warrant it. Many thanks, Rick Bensene
tmorris@convex.UUCP (08/26/85)
Sure , you can read the codes ! If you want to spend $350 ,
you can buy an ALCL scan , a handy device to read out your computer's
memory in digital form . What ? Don't want to spend $350 ? Then use
a paperclip ! Yes ,Virginia ,there is a way to dump the diagnostic
memory codes using a paperclip . Use a large size paperclip . Cut
it with dikes until it is shaped like this:
________________
\
________________/
Now ,flatten the two ends with a hammer. You now own a diagnostic
register reading tool. Get in your Camerooo ,and look just above your
right knee . There will be a removable plastic cover about 1x2" .
Remove it . You should see :
a b
[][][][][][][][][][][][][][]
[][][][][][][][][][][][][][] a conntector like this
With the ignition off , insert the paperclip fattened ends in locations
a and b . Turn on the ignition , and the check engine lite should flash a
code 12 .... that is flash............flash flash. It will do this three
times . What follows will be the real trouble codes .
Here are a few , if memory serves:
12 ................ no output from distributor (OK if engine
is not spinning)
13 .................. O2 sensor fault
14 .................. coolant sensor fault (short)
15 .................. coolant sensor fault (open)
23 ................... Mixture Control Solenoid fault
42................... dist. advance fault
45................... rich exhaust
51.................. PROM
55 .................. ECM
Everyone seems to like to play with these , but don't waste your
time trying to fix them. Many of these circuits are so sensitive that
using improper test equipment on a sensor can destroy it .Besides ,your
friendly dealer is obligated to take care of it for 5years or 50,000
miles .Don't alter anything that would void your coverage , as these
parts are expensive.
If you want to verify a problem to take to the dealer , and you read
a trouble code (besides 12 ) then disconnect the battery cable for 30 seconds.
This will erase the codes in memory . Drive the car and see if the fault
reoccurs . If so , read the code again and verify it is the same .Then
report the code and the driving conditions when the check engine lite came
on to the dealer.
I used to work on this system for a dealer. It can be quite frustrating
to attempt to chase down an intermittent code , so the information regarding
operating conditions when it occured is very valuable.
HAPPY MOTORING
.