Tests W/ Codes 2.5L V6: Diagnosis Saab 900 II

Testing For Continuity (Resistance Measurement)

1. Make sure that the component or cable to be checked is not live.
2. With the instrument set to measure resistance, connect the test leads to each end of the component or cable to be checked. In the wiring, the resistance should normally be less than 1 ohm. For components, the specified resistance should be obtained as a reading.

Testing For Continuity (Voltage Measurement)

1. Connect up the load, if any.
2. With the instrument set to measure voltage, connect the black test lead to a good ground and the red test lead to the wiring side (positive).
3. At the output of a control module or switch: take readings in the direction away from the component and proceed successively out towards the load. When the voltage reading drops to zero you have just passed the break in continuity.
4. At the input of a control module or load: take readings from the power source and proceed successively in towards the control module or load. When the voltage reading drops to zero you have just passed the break in continuity.

ISAT diagnostics

Communication between the MOTRONIC control module and an ISAT is possible via pin 55.

Communication is two-way and accordingly consists of both input and output signals.

With the ignition switch in the Drive position and the ISAT in communication with the system, the voltage applied to pin 55 should be about 10 V.

The diagnostics socket is located underneath the dashboard on the driver's side of the car.

Diagnostic trouble code table, MOTRONIC 2.8.1

DIAGNOSTIC TROUBLE CODE CHART

MOTRONIC functions without diagnostic trouble codes

Pins 1, 20 and 21 - Triggering of ignition coil, see IGNITION COIL .

Pin 9-Speed signal, see SPEED SIGNAL

Pin 46-Main relay, see MAIN RELAY

Pin 42-D/R input, see D/R INPUT

Pin 54-Throttle position signal to TCS And AF22 control modules, see THROTTLE POSITION SIGNAL TO TCS AND AF22 CONTROL MODULES

Pin 43 - Engine rpm output signal from control module, see ENGINE RPM OUTPUT SIGNAL FROM CONTROL MODULE

Scheme 49

Test readings, control module connections

Scope

Test readings and instructions for measuring signals and signal levels on the MOTRONIC control module are given in the following pages.

Some important points to remember

1. Unless otherwise specified, all voltage measurements should be made with all components connected and with the ignition switch in the Drive position.
2. Readings must be taken with a Breakout Box (BOB) connected between the control module and the control module connector.
3. Some readings are to be taken with the engine running at idling speed.
4. Several voltage levels must be regarded as guiding values. Your common sense should tell you whether a reading is correct or not.
5. If any test reading is obviously wrong, use the wiring diagram to trace the leads, connectors or components which you consider ought to be checked more thoroughly.

> = greater than; < less than; = approximately equal to; = alternating current

COMPONENT/FUNCTION TEST CONDITION CHART

Scheme 50

LAMP FLASH CODES REFERENCE CHART

Scheme 51

The new EPROM that has been developed for the ISAT enables a completely new command code system to be used when carrying out fault diagnosis on model year 1994 cars.

Up to now, a three-digit code has been used to obtain readings or activate signals and functions. Starting with M94 cars, this has been superseded by a system of menus in clear text which make it easy to select the desired "command" directly on the keypad.

The structure of the MOTRONIC system's command menus will be evident from the schematic arrangement on the next page.

We then see that there are eight main menus, five of them with a sub-menu containing different numbers of commands or functions.

These are

1. READ FUNCTIONS (see «READ FUNCTIONS»(ref-245066-S16768655562006101800000) )
2. ACTIVATE (see «ACTIVATE»(ref-245066-S05222781752006101800000) )
3. READ ON/OFF (see «READ ON/OFF»(ref-245066-S30566926112006101800000) )
4. INITIATE (see «INITIATE»(ref-245066-S10833658632006101800000) )
5. READ SYSTEM INFO (see «READ SYSTEM INFO»(ref-245066-S24650094402006101800000) )

Scheme 52

MOTRONIC fault diagnosis schedule

DIAGNOSTIC TROUBLE CODES (DTC) LIST

Scheme 53

Points To Note When Diagnosing Faults

It is impossible to give any general rules for the procedure to follow when diagnosing faults in each individual case. Depending on the fault symptoms and other information available, one method may be the best in some situations and another method best in others.

However, the following points may serve as guidance when diagnosing faults in the TCS system. Recalling them from time to time during the course of the work could prove to be of considerable help.

1. Do not forget to check the fuses.
2. Inspect connectors for corrosion on pins and contact surfaces, excessive play, looseness or anything else which may be the cause of poor contact or a deterioration in conductivity.
3. Before connecting a BOB into circuit, first check the voltage supply to pin 37 and make sure that pins 2, 14 and 24 are properly grounded.

Note that the main relay remains operated for a certain time after the ignition has been switched off, see MAIN RELAY .

Fault symptom

Reluctance to start, poorer driveability and high fuel consumption. CHECK ENGINE lamp (MIL) on.

CHECK ENGINE lamp on.

CHECK ENGINE lamp on, reluctant to start when engine cold.

CHECK ENGINE lamp (MIL) on.

CHECK ENGINE lamp (MIL) on

CHECK ENGINE lamp (MIL) on

Diagnostic procedure

1. Connect the ISAT, start the engine and run it at idling speed until it reaches normal operating temperature. Use the ISAT command "OXY SENSOR 2-4-6" in the "READ FUNCTIONS" menu to check the voltage of the oxygen sensor, which should vary between 0.1 and 0.9 V. Vary engine rpm to obtain faster voltage variations. If there is no voltage or if it does not vary with changing engine rpm, the fault probably lies with the oxygen sensor or a break in the signal lead between the sensor and the control module.
2. Unplug the front oxygen sensor's connector and take a reading on pin 1 of the signal lead connector to check whether the preheater element receives current from fuse 38. Also check whether pin 2 is properly grounded at grounding point G7P. Rectify any faults that may be present in the wiring.
3. Take a reading across pins 1 and 2 of the oxygen sensor connector to check the resistance of the sensor's preheating element. The correct resistance is 2.9-4.0 ohms. Note that the resistance will be higher the warmer the sensor is, since the sensor contains a PTC resistor. (At extremely high temperatures the resistance may rise to 10 ohms.) If the resistance is not correct, change the front oxygen sensor.
4. With the ignition switched off, connect a BOB to the MOTRONIC control module and cable. Start the engine and measure the sensor voltage by taking a reading across pins 47 and 10 of the control module. The voltage should normally vary between 0.1 and 0.9 V. In the event of no continuity in the sensor or wiring, the control module will utilize a fixed voltage of about 450 mV on pin 47. Check the lead between pin 47 of the control module and pin 4 of the oxygen sensor connector for shorting to ground/batt+. NOTE: If the voltage from the oxygen sensor is constantly high or constantly low, it may be because the fuel air mixture is too rich or too lean (diagnostic trouble codes P0174 and P0175). Check this before changing the oxygen sensor.
5. If no fault can be detected after carrying out the above checking procedure, clear the trouble code and drive the car on the road to check whether the trouble code is generated afresh. If it is, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

CHECK ENGINE lamp (MIL) on

If other diagnostic trouble codes are present, deal with them first.

1. Activate the ISAT command "ADAPT. SHORT 1-3-5" or "ADAPT. LONG 1-3-5" in the "READ FUNCTIONS" menu to see whether the engine is running on a lean or rich mixture. Lambda 1 corresponds to 0%on the ISAT. "ADAPT. SHORT" displays the current fuel-air mixture and "ADAPT. LONG" shows the mean value of the mixture over the past 15-20 minutes.
2. Clear all trouble codes and drive the car to check whether any trouble codes are generated afresh. It they are, continue as described below.
3. Check the following points: that the oxygen sensor's signal lead is not in contact with any HT lead that components of the correct type are fitted in the fuel system that no air leakage occurs in the induction system that fuel pressure is correct that battery voltage is correct that no leakage occurs in the exhaust system ahead of or behind the oxygen sensor that all grounding points in the system are OK
4. If no faults can be detected after carrying out the above checking procedure, clear all trouble codes and drive the car on the road to check whether any trouble codes are generated afresh. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

CHECK ENGINE lamp (MIL) on

If other diagnostic trouble codes are present, deal with them first.

1. Activate the ISAT command "ADAPT. SHORT 1-3-5" or "ADAPT. LONG 1-3-5" in the "READ FUNCTIONS" menu to see whether the engine is running on a lean or rich mixture. Lambda 1 corresponds to 0%on the ISAT. "ADAPT. SHORT" displays the current fuel-air mixture and "ADAPT. LONG" shows the mean value of the mixture over the past 15-20 minutes.
2. Clear all trouble codes and drive the car to check whether any trouble codes are generated afresh. It they are, continue as described below.
3. Check the following points: that the oxygen sensor's signal lead is not in contact with any HT lead that components of the correct type are fitted in the fuel system that no air leakage occurs in the induction system that fuel pressure is correct that battery voltage is correct that no leakage occurs in the exhaust system ahead of or behind the oxygen sensor that all grounding points in the system are OK
4. If no faults can be detected after carrying out the above diagnostic procedure, clear all trouble codes and drive the car on the road to check whether any trouble codes are generated afresh. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

Engine will not start, erratic running, misfiring. Diagnostic trouble code P0322 generated if engine fails to start.

Engine performance may be down.

Engine performance may be down.

Engine performance down

Scheme 54

1. Use the ISAT command "CAMSHAFT SENSOR ACTIVE" in the "READ ON/OFF" menu. With the ignition switched on, the ISAT should show "NO", with the engine running it should show "YES". If this is OK, proceed to point 6. If not, continue with the next point.
2. With the ignition switch in the Drive position, check whether voltage is present on pin 1 of the sensor connector (12 V). Also check that the ground connection on pin 3 is OK. If it is not, check the lead between pin 1 of the connector and pin 87 of the main relay for continuity/shorting. Also check the lead between pin 3 of the connector and grounding point G7S for continuity/shorting to +12 V. If voltage and grounding in the connector are OK, continue with point 3. If no voltage is present and the wiring is OK, proceed to point 6.
3. With the ignition switched off, connect a BOB. Do not forget to plug in the camshaft sensor's connector. WARNING: Before turning the engine over, unplug the four-pin connector from the ignition coil module to prevent the engine from starting. Turn the ignition switch to the Drive position, turn the engine over and take a reading across pins 8 and 14 to check whether the voltage varies between 0 and 5 V (5 V when the camshaft sprocket's "pimple" passes the Hall-effect sensor). Start the engine and run it at idling speed. Repeat the above test. A reading of about 4.5 V should now be obtained across pins 8 and 14. Camshaft position sensor, input to control module low/high, no continuity or shorting to ground/batt
4. It incorrect readings are obtained in the above tests, take a reading across pin 8 (on the BOB) and pin 2 of the camshaft position sensor's connector to check the wiring for continuity/shorting. Also check that the clearance between the Hall-effect sensor and the camshaft sprocket's "pimple" is not more than 1.5 mm.
5. If voltage is present on pin 1 of the sensor's connector and pin 3 is properly grounded, but no voltage reading was obtained when carrying out the test in point 2, change the Hall-effect sensor.
6. If no faults can be detected after carrying out the above diagnostic procedure, clear all trouble codes and drive the car on the road to check whether any trouble codes are generated afresh. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

Symptom

CHECK ENGINE lamp (MIL) on

CHECK ENGINE lamp (MIL) on

The engine runs on only five cylinders.

Note. In connection with these diagnostic trouble codes there will probably also be a trouble code for incorrect fuel-air mixture.

Scheme 55

1. Unplug the connector from the injector. With the ignition switch in the Drive position, check whether battery voltage is present across pin 87 of the main relay and pin 1 of the injector connector. If it is not, check the wiring between the valve and the relay.
2. Measure the resistance across pins 1 and 2 of the injector. The correct resistance is 15.9 ohms. Injector 1, output from control module low/high, no continuity or shorting to ground/batt+
3. Take a reading across pins 1 and 2 of the injector connector. With the ignition in the Drive position (engine switched off), there should be no current or pulses across these pins. Then start the engine and check that a reading of about 0.4 V is now obtained. If a reading of about 0.4 V is obtained across pins 1 and 2, proceed to point 6. If it is not, continue with the next point.
4. Check the wiring between the MOTRONIC control module and the injector for continuity/shorting.
5. If possible, drive the car to see whether any fault symptoms are still present. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

The engine runs on only five cylinders.

Note. In connection with these diagnostic trouble codes there will probably also be a trouble code for incorrect fuel-air mixture.

Scheme 56

1. Unplug the connector from the injector. With the ignition switch in the Drive position, check whether battery voltage is present across pin 87 of the main relay and pin 1 of the injector connector. If it is not, check the wiring between the valve and the relay.
2. Measure the resistance across pins 1 and 2 of the injector. The correct resistance is 15.9 ohms. Injector 2, output from control module low/high, no continuity or shorting to ground/batt+
3. Take a reading across pins 1 and 2 of the injector connector. With the ignition in the Drive position (engine switched off), there should be no current or pulses across these pins. Then start the engine and check that a reading of about 0.4 V is now obtained. If a reading of about 0.4 V is obtained across pins 1 and 2, proceed to point 6. If it is not, continue with the next point.
4. Check the wiring between the MOTRONIC control module and the injector for continuity/shorting.
5. If possible, drive the car to see whether any fault symptoms are still present. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

The engine runs on only five cylinders. Diagnostic trouble code possibly generated in the MIU system (fuel consumption).

Note. Signals from injector 3 are sent to the main instrument for calculation of fuel consumption. In the event of a fault, a fault is probably also generated for the main instrument. In connection with these diagnostic trouble codes there will probably also be a trouble code for incorrect fuel-air mixture.

Scheme 57

1. Unplug the connector from the injector. With the ignition switch in the Drive position, check whether battery voltage is present across pin 87 of the main relay and pin 1 of the injector connector. If it is not, check the wiring between the valve and the relay.
2. Measure the resistance across pins 1 and 2 of the injector. The correct resistance is 15.9 ohms. Injector 3, output from control module low/high, no continuity or shorting to ground/batt+
3. Take a reading across pins 1 and 2 of the injector connector. With the ignition in the Drive position (engine switched off), there should be no current or pulses across these pins. Then start the engine and check that a reading of about 0.4 V is now obtained. If a reading of about 0.4 V is obtained across pins 1 and 2, proceed to point 6. If it is not, continue with the next point.
4. Check the wiring between the MOTRONIC control module and the injector for continuity/shorting.
5. If possible, drive the car to see whether any fault symptoms are still present. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

The engine runs on only five cylinders.

Note. In connection with these diagnostic trouble codes there will probably also be a trouble code for incorrect fuel-air mixture.

Scheme 58

1. Unplug the connector from the injector. With the ignition switch in the Drive position, check whether battery voltage is present across pin 87 of the main relay and pin 1 of the injector connector. If it is not, check the wiring between the valve and the relay.
2. Measure the resistance across pins 1 and 2 of the injector. The correct resistance is 15.9 ohms. Injector 4, output from control module low/high, no continuity or shorting to ground/batt+
3. Take a reading across pins 1 and 2 of the injector connector. With the ignition in the Drive position (engine switched off), there should be no current or pulses across these pins. Then start the engine and check that a reading of about 0.4 V is now obtained. If a reading of about 0.4 V is obtained across pins 1 and 2, proceed to point 6. If it is not, continue with the next point.
4. Check the wiring between the MOTRONIC control module and the injector for continuity/shorting.
5. If possible, drive the car to see whether any fault symptoms are still present. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

The engine runs on only five cylinders.

Note. In connection with these diagnostic trouble codes there will probably also be a trouble code for incorrect fuel-air mixture.

Scheme 59

1. Unplug the connector from the injector. With the ignition switch in the Drive position, check whether battery voltage is present across pin 87 of the main relay and pin 1 of the injector connector. If it is not, check the wiring between the valve and the relay.
2. Measure the resistance across pins 1 and 2 of the injector. The correct resistance is 15.9 ohms. Injector 5, output from control module low/high, no continuity or shorting to ground/batt+
3. Take a reading across pins 1 and 2 of the injector connector. With the ignition in the Drive position (engine switched off), there should be no current or pulses across these pins. Then start the engine and check that a reading of about 0.4 V is now obtained. If a reading of about 0.4 V is obtained across pins 1 and 2, proceed to point 6. If it is not, continue with the next point.
4. Check the wiring between the MOTRONIC control module and the injector for continuity/shorting.
5. If possible, drive the car to see whether any fault symptoms are still present. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

The engine runs on only five cylinders.

Note. In connection with these diagnostic trouble codes there will probably also be a trouble code for incorrect fuel-air mixture.

Scheme 60

1. Unplug the connector from the injector. With the ignition switch in the Drive position, check whether battery voltage is present across pin 87 of the main relay and pin 1 of the injector connector. If it is not, check the wiring between the valve and the relay.
2. Measure the resistance across pins 1 and 2 of the injector. The correct resistance is 15.9 ohms. Injector 6, output from control module low/high, no continuity or shorting to ground/batt+
3. Take a reading across pins 1 and 2 of the injector connector. With the ignition in the Drive position (engine switched off), there should be no current or pulses across these pins. Then start the engine and check that a reading of about 0.4 V is now obtained. If a reading of about 0.4 V is obtained across pins 1 and 2, proceed to point 6. If it is not, continue with the next point.
4. Check the wiring between the MOTRONIC control module and the injector for continuity/shorting.
5. If possible, drive the car to see whether any fault symptoms are still present. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

Since incorrect battery voltage usually causes trouble in other system functions, these diagnostic trouble codes are for the most part generated together with other diagnostic trouble codes.

1. Activate the ISAT command "BATTERY VOLTAGE" in the "READ FUNCTIONS" menu. Check the battery and charging system and rectify any faults.
2. Check that the MOTRONIC control module supply voltage is correct on pins 18, 27 and 37, and that pins 2, 14, 19 and 24 are properly connected to a good ground.

Idle uneven, slow or fast

The CHECK ENGINE lamp does not light up when the ignition switch is turned to the Drive position.

1. Activate the ISAT command "CHECK ENGINE" in the "ACTIVATE" menu. If the lamp cannot be activated or does not light up when the ignition switch is in the drive position, continue with point 2.
2. With the ignition switched off, connect a BOB to the MOTRONIC control module. With the ignition switch in the Drive position, check whether the CHECK ENGINE lamp lights up when a jumper lead is connected across pins 14 and 22. If it does not, check whether the lamp receives any current. Also check the lead and connector for continuity between pin 22 of the control module and the lamp.
3. The CHECK ENGINE lamp should light up when the control module grounds pin 22 if a diagnostic trouble code is generated or always when the ignition is switched on. Take a voltage reading across pins 37 and 22 on the BOB. Battery voltage should be present when the ignition is switched on.
4. If no faults can be detected after carrying out the above diagnostic procedure, clear all trouble codes and drive the car on the road to check whether any trouble codes are generated afresh. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

Poorer shifting performance

1. The signal from the AF22 control module to the MOTRONIC control module, which is a request for torque limitation, is extremely short (about 250 ms) and may therefore be difficult to check. Connect the ISAT to the AF22 control module. Select "TORQUE LIMITATION" in the "ACTIVATE" menu. When activated, "TORQUE LIMITATION" sends a signal to the MOTRONIC control module. At engine speeds above 3000 rpm the MOTRONIC system will then retard the ignition briefly as "ordered" by the AF22 control module. If the torque reduction function works, it can easily be heard by the change in the engine note.
2. If no indication of torque limitation can be heard as described above, check the lead between pin 51 of the MOTRONIC control module and pin 13 of the AF22 control module for shorting to ground.
3. If the cause of the fault does not come to light after carrying out the above diagnostic procedure, and no trouble codes are generated in the AF22 system, clear any trouble codes in the MOTRONIC system and drive the car on the road to check whether the codes are generated afresh. If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

No A/C function.

1. Activate the "AC RELAY" function in the "ACTIVATE" menu and listen to check whether the A/C relay is working. If the relay works as it should, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) . If the relay does not work, continue as described below.
2. With the ignition switched off, connect a BOB between the control module and its cable. With the ignition switch in the Drive position and the A/C function activated, check whether current is present on pin 40 of the MOTRONIC control module. If it is, proceed to point 2. If it is not, check the A/C function as described in Service Manual 3:2
3. Start the engine and check whether the control module grounds pin 25 when current is present on pin 40 (delay in the control module for idling compensation). If the control module grounds pin 25, check the A/C function as described in Service Manual 3:2. If the control module does not ground pin 25, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

The CHECK ENGINE lamp lights up if a fault develops in the internal memory of the control module.

1. Carefully check all connectors in the control module's grounding and voltage circuits, and also check that all grounding points are properly connected to ground.
2. Clear the trouble code. If possible, start and drive the car on the road to check whether the code is generated afresh. If it is, change the control module.
3. If the car cannot be started and no other fault can be found, change the control module.

Engine misfires or fails to start

Scheme 61

1. If possible, start the engine and use the ISAT commands "IGNITION COIL 1+4", "IGNITION COIL 2+5" AND "IGNITION COIL 3+6" in the "READ ON/OFF" menu. If the control module sends trigger signals from pin 1 (cyl. 1+4), pin 20 (cyl. 2+5) and pin 21 (cyl. 3+6), the ISAT should show "ACTIVE" when each command is used. If the ISAT shows "INACTIVE", go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .
2. Remove the HT lead from any spark plug in cylinders 2, 4 or 6 and connect it to a test spark plug with a wide gap. Ground the spark plug and use the ISAT commands "FIRING CYL 1-4", "FIRING CYL 2-5" and "FIRING CYL 3-6" in the "ACTIVATE" menu. The spark plugs corresponding to the relevant commands should now produce a spark. If they do not, the relevant ignition coil is not producing ignition current. Check the leads between pins 1, 20 or 21 of the control unit and pins 3, 1 or 2 of the ignition coils. If none of the ignition coils produces ignition current, also check whether pin 4 of the coils receives current from fuse 17.
3. Unplug the ignition coils' 4-pin connector and use a voltmeter to take readings across pins 4 and 1, 4 and 2, and 4 and 3. With the ignition switch in the Drive position, the voltmeter should show about 12 V and on engagement of the starter motor it should fluctuate between about 4 and 6 V. If the readings are not OK, continue with the next point. If the readings are OK, check the resistance of the primary circuit in the ignition coils by taking a reading across pins 4 and 1, 4 and 2, and 4 and 3. The correct resistance is about 1 ohm. Also check the secondary windings by measuring the resistance across the HT lead outlets for spark plugs 1+4, 2+5 and 3+6. The correct resistance is about 12,000 ohms. If the resistance is not OK, change the ignition coil.
4. If no diagnostic trouble codes have been generated in the MOTRONIC system, also check that the control module is supplied with the correct voltage and that its ground connection is good. Also check that the crankshaft position sensor is in satisfactory working order, see «DIAGNOSTIC TROUBLE CODES P0322, P0336»(ref-245066-S12972254642006101800000) . If no faults have been detected after carrying out the above checks, change the control module.

Scheme 62

For a description of how the main relay works, see MAIN RELAY .

Check its operation as follows

1. Turn the ignition switch to the Drive position and measure the voltage across pin 2 of the IAC valve, for instance, and ground, or across pin 3 of the mass air flow sensor and ground, to check whether the relay has been energized. If current is present, the relay is OK if it also releases about five seconds after the ignition has been switched off. If no current is present, continue with point 2.
2. Lower the relay holder under the dashboard and connect a jumper lead between ground and pin 85 of the relay. Check whether the relay has been energized. To do this, check whether current is present on pin 87 of the relay. If the relay has been energized, proceed to point three. If the relay has not been energized, check whether current is present on pins 86 and 30 of the relay from maxi-fuse 2. If it is, remove the relay and measure the resistance across pins 85 and 86 of the relay coil. The correct resistance is about 60 ohms. If the resistance is not OK, change the relay.
3. Check the lead between pin 85 of the relay and pin 46 of the MOTRONIC control module for continuity.

With the ignition switch in the Drive position, also check whether current is supplied to pin 27 of the control module from fuse 17.

If it is, and the control module does not ground pin 46, go to Before Control Module Replacement .

Scheme 63

Scheme 64

1. Use the ISAT command "DRIVE SIGNAL" in the "READ ON/OFF" menu. The ISAT display should read NO in selector positions P and N and YES in all other selector positions.
2. Start the engine and check whether any major "dips" in idling speed occur when shifting from P or N to any of the selector positions 1, 2, 3, D or R. If this is the case, check whether current is present on pin 42 of the MOTRONIC control module when any of the selector positions R, D, 3, 2, 1 is engaged. If current is present, proceed to point 5. If it is not, continue as described below.
3. Check the operation of the automatic transmission, see «SERVICING - A/T»(ref-96974) . Also check the lead between pin 11 of the automatic transmission and pin 42 of the MOTRONIC control module for continuity/shorting.
4. With the ignition switched off, connect a BOB to the MOTRONIC control module. Start the engine and take a reading on pin 4 to see whether the voltage increases by about 0.5-1 V when any selector position is engaged. If the voltage increases but "dips" in engine idling speed occur, continue with point 5. If the voltage does not increase, proceed to point 6.
5. Check whether battery voltage is applied to pin 2 of the IAC valve. Also check the lead between pin 4 of the control module and pin 1 of the IAC valve for continuity/shorting. (Any faults here should cause diagnostic trouble code P1211 or P1212 to be generated.) Also check the mechanical operation of the IAC valve for binding, air flow, etc.
6. If "dips" in idling speed still occur when any gear is selected in spite of the above diagnostic tests having been carried out, If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

Scheme 65

Somewhat poorer idle air control when driving in stop-and-go traffic.

1. Connect the ISAT and activate the command "WHEEL SPEED RF" in the "READ FUNCTIONS" menu. Drive the car and compare the speed shown on the ISAT's display with that of the car speedometer. If the speeds coincide, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) . If the speeds do not coincide, continue with the next point.
2. With the ignition switched off, connect a BOB to the MOTRONIC control module and cable. Raise the car, turn the ignition switch to the Drive position and rotate the right-hand front wheel. The voltage measured across pins 9 and 14 should now change between 0 and 10 V. If it does not, continue as described below.
3. Check the lead between pin 9 of the MOTRONIC control module and pin 7 of the ABS control module for continuity/shorting.

If the lead is OK, check the output signal from pin 7 of the ABS control module. See DIAGNOSIS - AW50-40LE .

Scheme 66

Diagnostic trouble code P1785 generated in the AF22 control module or one of the diagnostic trouble codes P1406, P1407 or P1408 generated in the TCS control module.

1. Use the ISAT command "THROTTLE POSITION" in the "READ FUNCTIONS" menu and, with the ignition switch in the Drive position, check whether the ISAT shows about 9%in the idling position and steadily increases to 85-90%in the full throttle position.
2. With the ignition switched off, connect a BOB between the MOTRONIC control module and the cable. With the warmed-up engine switched off and the ignition switch in the Drive position, check that a 100 Hz PWM signal of 0.25-1.0 V is present on pin 54. Start the engine and check that the voltage applied to pin 54 is: about 1.2 V at idling speed about 2.0 V at 2500 rpm about 12 V at full throttle.
3. If the signal is absent or not OK, check the throttle position sensor, see «DIAGNOSTIC TROUBLE CODES P0122, P0123»(ref-245066-S13580720442006101800000) .
4. If the throttle position sensor is OK and the signal from pin 54 is absent or not OK, If so, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

Scheme 67

Diagnostic trouble codes generated in the MIU, TCS and/or AF22 systems

1. Start the engine and use the ISAT command "ENGINE RPM SIGNAL" in the "READ ON/OFF" menu. If the control module sends out engine rpm signals, the ISAT display should read "ACTIVE". If the ISAT display reads "INACTIVE", go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .
2. If the ISAT display reads "ACTIVE", clear all diagnostic trouble codes in the MIU, TCS and/or AF22 systems and drive the car to see whether any are generated afresh. If they are, continue as described below. With the ignition switched off, connect a BOB to the MOTRONIC control module and cable. Check that there is a signal of about 6.5 V and 40 Hz on pin 43 at idling speed. At 2500 rpm the signal should be about 6.5 V and 125 hz. If the signal is OK, the fault lies either in the leads connected to the MIU, TCS and/or AF22 control modules or in any of these systems. If there is no output signal on pin 43, it may be on account of a short circuit to ground/batt+ in any of the leads connected to the above systems. Rectify any faults. If there is no short circuit, go to «Before Control Module Replacement»(ref-245066-S27707632572006101800000) .

Scheme 68

When all tests have been carried out according to the relevant diagnostics procedure or by manual fault diagnosis without any faults having been found, it is natural to assume that the control module is at fault.

In view of the fact that the control module is an exceptionally high-quality component and also extremely expensive, it is important to verify the diagnosis as far as possible.

Therefore, go through all the points very carefully before definitely pointing to the MOTRONIC control module as the cause of the fault.

1. Check once again that every single point in the fault diagnosis program of the relevant diagnostic trouble code has been carried out.
2. Study the wiring diagram of the circuit in question and make sure you understand how it works. Relevant parts of the technical description and the electrical descriptions of operation in Service Manual 3:2 "Electrical system" may be of assistance in this respect.
3. Check all grounding points. If you have already done so, do it once again. Check that power ground and signal ground are electrically separate.
4. Check the voltage supplied to the control module.
5. Go once more through each point listed under "Points to remember" on page 77.
6. If the original fault still persists in spite of this, then the MOTRONIC control module will have to be replaced.

Scheme 69

All control modules are more or less sensitive to static electricity and, if handled carelessly or incorrectly, may be damaged so seriously that they no longer work properly. It is therefore important to ensure that the following rules are observed at all times when a control module is removed or replaced for any reason.

Scheme 70

1. Avoid unplugging or removing a control module unless absolutely necessary.
2. Never touch the connector pins and never place the control module in such a way that the connector pins may come into contact with foreign objects.
3. Before unpacking a new control module, ground the packaging to the car body. Open the packaging as shortly as possible before installing the control module.
4. When handling or working on control modules it is important to ground yourself from time to time. This is particularly important when you have been sitting in the car, when changing your position, or when moving round the car. It is even more important in a climate with extremely dry air (e. g. during the winter in cold markets).
5. Avoid wearing clothes made of synthetic (man-made) fibres.
6. Furthermore, always handle control modules which are suspected of being defective in the same manner. This will greatly improve the chances of determining the cause of the fault.

Scheme 71