APC Solenoid - Chatters At Idle
87saab02FILE IN S.I. Man VOL. I
SEC. A-2 PG. 202
Service Information
SUBJECT: CORRECTING APC SYSTEM INTERFERENCE ISSUE: 08/87-989
APPLICATION: 1986-87 900 TURBOS
Electrical interference at the knock detector wire and faults in the APC wiring harness can cause chattering of the APC solenoid at idle. This procedure deals with correcting coaxial knock detector wire interference by taking the wire out of the engine wire harness and routing the wire by another way within the engine compartment.
Before rerouting the coaxial knock detector wire, faults in the wiring circuit should be corrected, if necessary. Check the APC system ground points at the left inner fender and at the radiator crossmember. The grounds must be tight and clean. The APC system transducer and vacuum switch should also be checked for function. A failure in either one can cause solenoid chatter at idle.
Rerouting of the knock detector wire involves the replacement of the wire.
Knock Detector Wire 95-61-804
FIGURE 1 - REMOVING THE INSULATOR STRIP FROM THE APC CONTROL UNIT.:
Knock Detector Wire Removal
1. Disconnect the negative (-) battery lead and cover the terminal post on the battery.
2. Remove the bracket for the APC system control unit from the fender and unplug the 25 pin connector.
3. Remove the cover over the left headlight, rubber moulding from the right hand side of the intercooler, air mass meter and the left front turn signal assembly.
4. Disconnect the bottom hose from the AIC valve and the top hose from the throttle housing.
5. Open the 25 pin connector and remove the rubber seal. Slide back the rubber, cut off the cable tie and pull out the connector block.
Remove both pin insulator strips. See Figure 1.
FIGURE 2 - DISCONNECTING THE WIRE LEADS.:
6. Disconnect the following leads complete with pins from the Connector block. See Figure 2.
488 pin 16 GN 489 pin 17 BR 490 pin 4 shielded
FIGURE 3 - CUTTING OFF THE LEADS.:
7. Cut off the disconnected leads where they enter the wiring harness. See Figure 3.
FIGURE 4 - CUTTING OFF THE KNOCK DETECTOR WIRE.:
8. Unplug the two-pin connector from the knock detector.
9. Cut off the knock detector wire where it enters the wiring harness. See Figure 4.
Knock Detector Wire Installation
1. Install the new knock detector wire by first plugging into the knock detector. Install tubing over the terminals on the control unit end of the knock detector wire and secure with tape. This prevents damage to the terminals and facilitates routing of the harness.
FIGURE 5 - REROUTE THE WIRE AND SECURE LOOSELY WITH CABLE TIES.:
Run the knock detector wire alongside the engine wire harness at the starter motor. See Figure 5.
Secure the wire with cable ties but do not overtighten them. Overtightening can damage the coaxial knock detector wire.
FIGURE 6 - FITTING THE WIRE LEADS.:
2. Pass the end of the wire lead through the rubber and connector cover and remove the tubing and tape.
3. Fit the wires into the connector. See Figure 6.
488 pin 16 GN 489 pin 17 BR 490 pin 4 shielded
FIGURE 7 - REFITTING THE PIN INSULATOR STRIPS.:
4. Refit the pin insulator strips into the connector and push the connector block back inside the cover as shown in Figure 7. Secure the harness with a cable tie and slide the rubber back into position.
Refit the rubber seal.
5. Plug the connector into the control unit for the APC system and bolt up the control unit bracket to the fender.
6. Refit the air mass meter, left front turn signal assembly, bottom hose to the AIC valve and the top hose to the throttle housing.
7. Refit the rubber moulding to the right-hand side of the intercooler.
8. Refit the cover over the headlight.
9. Reconnect the battery.
10. Test drive the car and ensure that the APC system is functioning properly.
Warranty Information: For warranty claims, use Failure Code 37164-68-0-01-
05. Labor time allowance is 0.8 hour which should be entered as straight time on the claim.