Ionization Detection Module (740): Connection: Notes

IONIZATION DETECTION MODULE - CONNECTION DESCRIPTION

Pin No.	Signal type	Description
1	Ignition trigger cylinder 4, in	Synchronization of ionization current measurement for cylinder 4
2	Ignition trigger cylinder 3, in	Synchronization of ionization current measurement for cylinder 3
3	Knock signal, out	Knock signal, raw value to ECM
4	Combustion signal 1, out	Combustion signal, raw value to ECM
5	n/c
6	n/c
7	Ionization signal 2, in	Ionization signal from ignition coil cylinder 2
8	Ionization signal 3, in	Ionization signal from ignition coil cylinder 3
9	Ignition trigger cylinder 1, in	Synchronization of ionization current measurement for cylinder 1
10	Ignition trigger cylinder 2, in	Synchronization of ionization current measurement for cylinder 2
11	Combustion signal 2, out	Combustion signal, raw value to ECM
12	B+	Power supply B+ from main relay
13	B-	power supply B- from grounding point G7
14	n/c
15	Ionization signal 4, in	Ionization signal from ignition coil cylinder 4
16	Ionization signal 1, in	Ionization signal from ignition coil cylinder 1

Fig 1: Identifying Communication Flow - Ionization Detection Module (1 Of 3)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Identifying Communication Flow - Ionization Detection Module (2 Of 3)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 3: Identifying Communication Flow - Ionization Detection Module (3 Of 3)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

CDM performs an initial processing of the ionization signal from each ignition coil. CDM generates a common knock signal from the ionization information of the four cylinders. This signal is used by ECM to evaluate engine knocks.

After the spark has been fired, ECM " listens" to the knock signal of each cylinder over a certain number of crankshaft degrees, known as " windows" .

The ionization signal is bandpass filtered to filter out the part of the signal containing knock information.

Knock information is characterised by " ringings" which are oscillations in the ionization signal. To obtain the combustion signal, the ionization signal passes a low-pass filter, where relatively slower oscillations pass through.

These ionization signal oscillations make up the part containing information on combustion quality.