Crank Mounted Hall Effect Sensor - Diagnosis
File INS.I. Man.
VOLUME
I
SECTION
B-3
PAGE
23
ISSUE
08/89-1169
SUBJECT:
DIAGNOSIS OF CRANKSHAFT-MOUNTED HALL EFFECT SENSOR
APPLICATION:
1989- 900, 900S, AND 9000S MODELS
Hall-Effect Sensor:
Beginning with 1989 models, the Hall-effect sensor for the EZK ignition system is mounted at the crankshaft pulley (Figure 1). This sensor consists of a semiconductor element in conjunction with a magnet. A shutter wheel mounted on the back of the crankshaft pulley interrupts the magnetic field, determining the ignition timing.
HALL-EFFECT SENSOR DIAGNOSTIC PROCEDURE
TOOLS REQUIRED:
Digital Volt/Ohm Meter (VOM)
Timing Light
Make the following checks at the back of the electrical connector for the EZK control unit. Use a high resistance digital Volt/Ohm Meter (VOM or a logic probe. Switch the ignition to the "ON" position.
Voltage Check:
1. Connect the VOM between terminal 10 and terminal 4 (Figure 2). This measures the voltage supply to the Hall-effect sensor on the crankshaft. The reading should be approximately 1OV or more (battery voltage).
Signal Voltage Check:
2. Connect the VOM between terminal 24 and terminal 10 (Figure 3). This connection measures the signal from the Hall-effect sensor.
3. Turn the key to the "on" position. Slowly turn the engine over by hand. The meter reading should be less than 0.4V (shutter wheel in the open position) or greater than 3.0V (shutter wheel in the closed position).
4. If the above readings are incorrect, check the wiring harness and connectors. Replace the crankshaft sensor if readings indicate a faulty sensor.
NOTE
For a complete EZK ignition system troubleshooting guide, see the plastic coated card, "No Start" Ignition Fault Tracing Procedure, distributed with the June 1989 issue of Technical Tips.
5. If the engine runs, but does so erratically or with poor performance, connect a timing light and check the ignition timing at idle. The timing should hold steady at 14° 8TDC.
6. Next check the timing with the engine speed above idle. The timing may advance, but once advanced it should not vary.
7. If at any time the timing marks appear to be moving back and forth erratically, the Hall-effect sensor should be inspected. It is likely that the spring which holds the magnet in place has broken, causing the timing variance and the resulting poor engine performance.
WARRANTY INFORMATION:
For warranty repairs where the above diagnostic procedure is indicated, use Labor Operation No. 12314, Diagnostic Time-Ignition Crankshaft Sensor 0.3-hour, 89-. Readings must be included in the claim text. Saab-Link (DCS) Dealers: Add this operation to your Labor Operation Table.