Testing SAAB 9000 Direct Ignition – Pattern Failures
The SAAB Direct Ignition (DI) system is used in many SAAB vehicles from 1989 to the present. DI is a multispark ignition and sensor system. The Ignition Discharge Module (IDM) is commonly referred to as the “ignition cassette.” The IDM is a one-piece, four-coil unit, with the ignition coils permanently mounted in it. The metal IDM is bolted to the valve cover and provides shielded protection from radio interference. The earliest IDM had two pigtail harnesses that attached to two connectors near the battery. Most of the early IDMs have been replaced by an adapter harness and a later version of the IDM with a 10-pin connector on the IDM itself.
To test the late IDM for a no-spark condition, it is necessary to have spark plugs in each coil. Ground the spark plug threads with jumper wires before testing to avoid damaging the IDM with high voltage flashover. Test that battery voltage is applied to pin 10 of the rectangular 10-pin connector when the ignition key is on and also when cranking. The power comes from the injection power supply relay located in the relay panel above the glove box. There must be a full-time ground on pin 6 of the IDM connector.
The source of trigger pulses for the coils depends on the system used on the particular car. The early DI system, used with the Bosch LH Jetronic Injection system, has its own Ignition Control Module (ICM). The later turbo models are equipped with the Trionic system that incorporates fuel injection, ignition and turbocharger boost control functions into one control unit. When the starter is engaged, the ICM or the Trionic module provides an individual trigger pulse to each of the cylinders. To verify that this 12-volt ground pulse is present, connect a standard timing light to the battery and attach the inductive pickup of the timing light to each of the four trigger wires in turn. Cylinder #1 is pin 2. Cylinder #2 is pin 3. Cylinder #3 is pin 4 and Cylinder #4 is pin 5. When the starter is engaged, each of the triggers should flash the timing light. If you have verified that power, ground and all triggers are present, but there is no spark output at the plugs, a new IDM is needed.
If there are triggers for some cylinders and not others, the 1CM or Trionic module may be at fault. Test the continuity of the trigger wires. If there are no trigger pulses to the IDM, test for injector pulses. If there are no injector or trigger pulses, suspect the Crank Position sensor (CKP). Early cars use a Hall sensor located behind the crank pulley. On these models, there is a three-pin, pigtail connector accessible near the alternator, under the intake manifold. One of the outer two wires should have full-time ground and the other outer wire should have over 10 volts when the key is on. The center wire is for the signal and should switch between five volts and ground as the crankshaft rotates. The reluctor for the CKP has two wide gaps and one very narrow gap, presenting a unique scope pattern. Later models use an inductive sensor in the forward-facing side of the block, near the bell housing. The inductive CKP has an output of approximately 1.5 to 3.0 volts AC when the starter is engaged.
It is possible for the DI system to set a Camshaft Position sensor (CMP) code. Careful inspection will show there is no CMP on the car. The position is determined by the location of the CKP and by the synchronization circuit in the IDM. The spark plugs have a constant 80 volts applied to them. The IDM and ICM/Trionic modules use the ionization characteristics of the .040 in.-gap spark plugs to determine which of the paired cylinders is at its combustion stroke and which is at its exhaust stroke. The signal for cylinders #1 and #2 is carried by pin 8 and the signal from cylinders #3 and #4 is carried by pin 9. The synchronization circuit will have an alternating five-volt ground pulse in the 0.30 millisecond to 0.70 millisecond range at idle. This system works best with standard center electrode spark plugs. An unusual voltage variation across the spark plug gap can set a CMP code. The standard spark plugs have approximately 5,000 ohms resistance.
The Trionic system uses an additional signal at pin 7 as an engine knock detection circuit. As with the CMP code, you may have a knock sensor code when there is no obvious knock sensor. The knock signal is approximately 50-100 millivolts ACV at idle, and 300 millivolts ACV would be considered a large amount of knock. Installing the correct spark plugs will often cure knock code symptoms.
As a safety matter, remember that when the ignition key is turned off, the burn-off function of the IDM will be activated. For five seconds, more than 1,000 sparks will fire across each spark plug to burn it clean. This is more ignition power than you would ever experience on a running engine, so be careful!
Written by Daniel Winterhalter IDENTIFIX European Team Leader. Daniel is a four-time winner of the Saab National Master Competition, with 24 years of Saab dealership experience as a technician, foreman, and service manager.
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