Model 140
In model 140, the left front ABS wheel speed sensor (L6/1) generates a sine wave vehicle speed signal directly proportional to vehicle speed. The ABS (or ABS/ASR) control module (N30 or N30/1) transmits a square wave signal of corresponding frequency to the instrument cluster. So a precondition for this test is that the ABS (or ABS, ASR) system functions normally. The Service Microfiche does not yet include testing procedures. Use the following test procedure:1. Remove instrument cluster.
2. Unplug connector 1.
3. Test the speed signal output of the ABS or ABS, ASR control module (N30 or N30/1) with the multimeter set to AC volts. Connect the multimeter to socket 12 (signal) and socket 10 (ground). Lift the left front wheel and spin it at least 1 rev./sec. The speed signal must be > 4.0 volt AC. Using the signal generator/frequency counter, check that the speed sensor output frequency increases in direct proportion to wheel speed.
4. Check the speedometer power supply at the harness connector with the multimeter set to DC volts.
Measure the voltage between socket 1 (circuit 15, fused) and socket 10 (ground) on harness connector 1, with the ignition switch in position 2. Nominal value is battery voltage.
5. Reconnect connector 1 and partially reinstall instrument cluster. Set the signal generator to produce a square wave > 10.0 volts AC. Connect the signal generator to the speedometer at connector X35/7 (see Figure 3): red wire from signal generator to socket 7 of connector X35/7, black wire from signal generator to ground.
6. Confirm the vehicle model tested. Set the frequency output of the signal generator according to Table 1. Test the speedometer at all 3 frequencies listed. The speed indicated must fall within the tolerance range shown.
Note:
Perform this test as quickly as possible, since miles are being added to the odometer.
7. Reconnect and reinstall the instrument cluster, and verify proper operation of all instruments. Check and clear all DTCs that may have been set during testing.