How to find engine codes

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.

These are not valid fault codes, valid codes have the Letter "P" "U" or "C" followed by four numbers, so a typical Standard OBD2 fault code for the engine would be PXXXX, the "X": being a number 0-9 and the "P" standing for "powertrain"

What is year--make--model and engine size?
How long since a tune-up? Are there any applicable trouble codes? With gasoline engine, if your saying no spark, have to check spark plug wires--spark plugs--ignition coil, primary voltage and ground for the ignition coil or coil pack.
Also, test with engine cranking, spark--proper fuel pressure and fuel injector pulse. If your missing all three have to check for rpm signal.

From a reputable repair website:


P0351 - OBD-II Trouble Code

Auto Systems and Repair

Ignition Coil "A" Circuit Primary/Secondary Malfunction Our emissions expert has put together the following information about the P0351 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code

• OBD II P0351 Ignition Coil "A" Circuit Primary/Secondary Malfunction

What does this mean? The ignition coil or coils are responsible for igniting the air/fuel mixture inside the combustion chambers. Without reliable performance from the ignition coil(s) the vehicle will stumble and misfire.
Code P0351 indicates there's an electrical problem in either the primary ( the computer side ) or the secondary ( the spark plug side ) of the Ignition Coil "A" Circuit.
Symptoms

• Check Engine Light will illuminate
• Engine idles rough
• Engine misfires on acceleration
• In rare cases, the engine may not exhibit noticeable symptoms

Common Problems That Trigger the P0351 Code

• Defective Ignition Coil(s)
• Defective Spark Plug(s)
• Intake Manifold Vacuum leaks
• Carbon buildup in the Throttle Body air passages
• Defective Idle Air Control Valve or Electronic Body

Common Misdiagnosis

• Ignition coil(s) replaced when cause of the malfunction was a vacuum leak
• Spark Plugs replaced when cause of the malfunction was a vacuum leak

no spark from coil directly?
is the cam turning, is the dizzy rotor spinning. ????

check all fuses first. Ig-coil, FI and dome.
then using diagnostic jumper wire or fuse, (as approp)
crank engine look for code 41 o 42.!!!

USA cars , answers only
our cars are all EFI that year.
no engine swaps to Suzuki G16A/B sidekick or tracker engines.!
1: engine cranks
2: no spark
3: The ECu makes spark
the CMP sensor in the DIzzy , (never fails if rotor turns, does rotor turn, if not cam belt igored and now snapped.)
the cam turns. the CMP fires. the ECU takes this CMP signal
and fires the ignitor next to coil and the coil charges, and release and BAM spark.

that is it.
the ECU will tell you when the CMP dies or the Ignitor fails
why not ask it.
1: key on
2: diagnostic jumper in place (flashes 12s for ok)
3: crank engine,for 5sec, not 1 ,not 2.
3: release key not off.
4: see code 41, or 42, BINGO !@!!!!

The code indicates the coil pack or spark plug is malfunctioning. You can test this using an additional person. by removing the coil pack and spark plug, place the spark plug into the coil pack and ground the tang on the spark plug to the engine. Have someone start the engine and watch for a blue spark. if there is no spark, then the coil pack is malfunctioning. There is also ways to check the coil packs using a multimeter.

also, bee sure you didnt crack the ceramic part of the plug during initial installation.

INSPECTION

1. Disconnect high-tension code from spark plug.
2. Remove the spark plug.
3. Connect the spark plug to a high tension code.
4. Hold the spark plug with insulated pliers 5~10mm from a ground.
5. Crank the engine and verify that there is a strong blue spark.
If there is no spark, inspect the following points.

Step Inspection Action

1 Check for good connection of ignition coil Yes Go to next stop.
No Repair or replace
2 Check if resistance of high-tension leads are OK Yes Go to next step.
No Replace
3 Check if the ignition coil is electrically charged
1) Ignition switch "ON"
2) Check if the engine coil (+) is electrically charged
Yes Go to next step
No Check the wire harness between ignition switch ignition coil and ECM
4 Check if resistance of ignition coil is OK
Resistance
Primary : 0.36~0.44Ω (at 68°F (20°C))
Secondary : 10.9~13.3kΩ (at 68°F (20°C)) Yes Go to next step
No Replace
5 Check if ECM is OK Yes
No Replace

REMOVAL

Do not attempt any maintenance on spark plug if engine is hot.
1. Disconnect negative battery terminal.
2. Carefully remove high-tension leads.
3. Use compressed air to blow any dirt or debris from around spark plug hole.
4. Check that spark plug fits squarely in spark plug socket and remove spark plug.

Raise a vehicle and install SST(OK552 131 001) in order to replace cylinder 2, 4, 6 spark plug.

INSTALLATION

1. Install spark plug into cylinder head.

Tightening torque : 18~22lb-ft (25~30N·m, 2.5~3.0kg-m)

2. Reconnect high-tension leads.
3. Reconnect negative battery cable.

the valve cover seals like to leak and fill up the spark plug tubes with oil. so 1st thing, you should pull the spark plug boots to check, the pull and inspect the spark plugs.

next.
pull spark plug boot off of the #1 spark plug. Insert a new spark plug into the spark plug boot. Ground the plug to the engine.
Crank the engine and look for spark across the electrodes of the spark plug.



then reconnect the boot the the #1 plug, pull the boot off of the #2 plug repeat the test, then do #3 and #4.

if all cylinders have no spark/ weak spark, its most likely a bad coil pack.

to check the coil pack:
Measure the primary resistance of each coil. At the coil, connect an ohmmeter between the B+ pin and the pin corresponding to the cylinders in question. Resistance should be 0.45 - 0.65 ohm.

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Measure the secondary resistance of the coil between the towers of each individual coil. Secondary resistance should be
11k - 14k ohms