[MT-2500]

If equiped with the VCM computer system .
Here is the first test.
MT

ENHANCED/HIGH VALUE IGNITION SYSTEM (080-11)

NOTE: This system is used on "S" and "T" Series with 4.3L engine equipped with VCM-A controller. Timing is not adjustable on this system.

Spark
1) If equipped with factory tachometer, disconnect tachometer terminal before performing tests. To disconnect tachometer lead, it is necessary to disconnect the Gray ignition coil connector from ignition coil. Using a fused jumper wire, jumper connector terminal"B" of ignition coil and Terminal Test Adapter Kit (J 35616-A).
2) Using Spark Tester (ST -125), crank engine and check for spark at coil wire and at each spark plug wire. If spark is not
present or intermittent, go to next step. If spark is present, check spark plugs and fuel system.
3) Check coil wire or spark plug wire resistance on suspect wire. Resistance should be about 1000 ohms per inch.

Ignition Coil Power Source
1) Turn ignition off. Disconnect ignition coil driver module connector. Turn ignition on. Using DVOM, check voltage at ignition coil driver module terminals "A" and "0". See Fig. 5. Both terminals should read 10 volts or greater. If voltage is as specified on both terminals, go to next step. If voltage is 10 volts or less on either or both terminals, go to step 6).
2) Place DVOM on AC scale. Connect DVOM to ignition coil module terminal "B" and ground. Crank engine. Voltage reading should be 1-4 volts. If voltage reading is as specified, go to next step. If voltage reading is not as specified, go to step 4).
3) Connect test light to battery voltage and probe coil
driver module connector terminal "C". See Fig. 5. If test light illuminates, check for faulty ignition coil driver module connection or faulty ignition coil module. If test light does not illuminate, check for open ignition coil driver module ground.
4) Turn ignition off. Disconnect Gray VCM-A harness
connector. Check for continuity between VCM-A ignition control connector terminal and ignition driver module connector terminal "B". If continuity is present, go to next step. If continuity is not
present, check for open IC circuit between VCM-A and ignition coil driver module.
5) Connect test light to battery voltage and probe VCM-A ignition control harness terminal. If test light illuminates, check
for grounded IC circuit between VCM-A and ignition coil driver module. If test light does not illuminate, check for faulty VCM-A connection or VCM-A.
6) If voltage is less than 10 volts on both terminals, check for faulty ignition feed circuit to ignition coil, grounded external coil circuit or faulty ignition coil. If voltage is less than 10 volts
on only one of the terminals, check circuit from affected terminal or check for faulty coil connection or faulty coil.