10.14 - Ignition amplifier module ( Dana Haydel,
The amplifierís job is to pulse the ignition system to fire off each spark plug. This performs the job of the points on the older model years.
The amplifier is located directly below the ignition coil. The ignition coil needs to be removed for access. Due to its location when there are ignition related problems it is worth the while to clean these components and connectors. A good quality electrical cleaner typically takes care of these problems. Make sure the electrical contact clips and blades are also cleaned. This area tends to collect a lot of grease, oil, and dirt. Be sure when re-assembling the amplifier module that di-electric grease is used on the back of the module where it bolts to the plate.
Ignition amplifier schematic is located in Section 6.20 ECU Wiring Diagram.(the schematic should be linked)
Make sure battery voltage is 12V+ for testing otherwise results may look like failed actually exist due to low voltage.
Ignition amplifier checks:
Positive (+ , white/pink wire) side of ignition coil should be hot at 12V (it's connected to battery via relay). Same wire goes to ignition amp B+ pin. Remember that battery voltage will drop when engine cranks.
Negative (- , white/black wire) side of coil goes to C- pin of amp. This should also be at battery voltage when not cranking. This is the line the amp normal pulses to ground and then opens to fire a spark (where the points would be on an old car). If you have battery voltage when NOT CRANKING measure voltage between battery + and this line - should be small not cranking and then rise. If it doesn't rise start suspecting amp module and carry on tests.
The B terminal (white/green wire) on amp should be around 5V above ground (Mr. ECU drives this one).
The E terminal (white/red wire) on amp goes to ECU (-) should rise when cranking. If this does not rise, disconnect amp module and repeat test. If it rises the amp is bust (take out and replace the GM module assuming you don't find a more obvious cause). If it doesn't rise you have to check back to ECU.
Another method that may be useful in determining an amplifier problem is to use a timing light on the high tension lead and each of the ignition wires. Observe for a consistent spark at a relative consistent interval. Again low voltage from the battery can produce a non consistent spark.
Observe the engines RPM gauge on the dash, typical while cranking the meter's pointer will pulse while trying to start. This isn't all inclusive but does tend to indicate the amplifier is functioning.