I have a 1994 chevy suburban i'm trying to find the 'service code' when i 'jumper' the A to B plug under the dash. it says the service lite will 'flash 1 time for one problem, 2 times for another and so on ... Please help if you can. Thank you

no spark at all spark plugs and the main spark COIL 1 terminal?
1994 is old car, old old Chevy OBD1 PCM.
check all fuses first
then see the service manual, to do the DLC jumper wire trick
to get the FLASH codes out of the PCM.(ECM)
steps
The Assembly Line Diagnostic Link (ALDL) connector or Data Link Connector (DLC)
jumper A to B
KEY ON, not started
The Service Engine Soon or Check Engine light should be flashing.
if CEL lamp bulb is dead,it must be replaced.in IP cluster
The code(s) stored in memory may be read through counting the flashes of the dashboard warning lamp. The dash warning lamp should begin to flash Code 12.
Code 12 NOT and error, all others seen are DTC errors.
if none happen crank engine for 5 seconds,release key see errors now.
42/43 code bad spark see manual
21./22 bad TPS

not told you is what the big spark coil does all by itself
if your Distrib has HEI, the coil main HV is buried inside..
tricky to test.
if spark really dead. the whole rebuilt distrib is best.cure.
NO ENGINE of 5 told and is an Engine question, above is 94 generic.
here are 4 gas engines then with external spark coil pack
we take a new spark wire and plug.
connect it to HVcoil pack tower lugs.
ground the spark plug shell
and crank test the coil,for spark if fails
bad fuses
bad dizzy
bad ecm
or bad coil and is less cost than all but fuses.

you may not have codes some problems dont cause trouble codes --bad catalyic converter --tune up needed--egr valve --fuel filter --fuel pump failure -to name a few

check fuse link near starter motor

1994 Chevy suburban during these years the alarm was after market , your best option is to remove the alarm,it installed under the dash at the steering column,the only wire they used was starter wire at the ignition with a relay connected to the transponder,there is a way around look for a small push button and press it hold it and crank the engine this bypass is hidden under the dash and can be in varies places

there is a 20 amp fuse in the fuse block that feed these circuits

Check the wire harness on the transfer case to make sure it's still plugged in. Check the selector switch in the dash. Check the hub sensor wire harnesses on the front wheels.
Check for error codes through OBD-II connector under the dash.
Good luck.

did you get an answer to this question?
Basically you need the DRAC out of the donor vehicle. It is located behind the glove box. 3"x3" square box. Depending on axle gear ratios and tire size you may need to change the jumper settings to allow your speedometer to read properly. This is a very simple procedure.
To convert any 88 and later to the 94 dash you will need not only the drac but get it's harness with at least 6" of its wiring as well.
You will need the 94 dash plug also with at least 6" of wiring on it too.

I have had that feeling in my 95 Blazer and it turned out to be a $15 fix. It was the U-joint. Crawl under there and wrap your hands around the drive shaft. Rotate it back and forth. If there is a lot of slop, then it is the U-joint.

1. Locate the Data Link Port. It is located under dash drivers side. Be sure you know
which pins are 8 and 4.


(Note port is wider at top) Your OBDII port will not
have numbers, use the for reference.






2. Make sure there are metal contact pins in terminals 8 and 4. Connect 8 to 4 with a
suitable jumper wire (leave the jumper wire connected throughout the programming
procedure). Make sure you know which terminals are 8 and 4. The vehicle will respond
by locking and unlocking the doors to signify entering of programming mode.
3. Press and hold both the LOCK and UNLOCK buttons together on the first transmitter to
be programmed. After about 15 seconds, the vehicle will respond by locking and
unlocking the doors. Release the buttons on the transmitter.

4. Within one minute, repeat the previous step on the remaining transmitters to be
programmed.

5. Remove jumper wire applied to the OBDII Port.

Powertrain Control Module = under right side of dash, near blower motor.
Engine Control Module = same as above
Vehicle Control Module = same as above

All Suburban vehicles are equipped with only one of these choices. Good luck.