Turbocharger - Unwanted Boost Pressure Reduction
89saab03FILE IN VOL.
S.I. Man I
SEC. B-2 PG. 20
SUBJECT: CORRECTING APC SYSTEM INTERFERENCE ISSUE: 04/89-1141
APPLICATION: 9000 TURBOS 88- EARLY 89
In some cars, electrical interference from the "hot" feed for the ignition system
and from the lead carrying the ignition pulse can adversely affect the signal
carried in the coaxial knock detector cable. The ECU for the APC system may
interpret this interference as engine knock signals, resulting in an unwanted reduction in boost pressure.
If, when determining the cause of the engine being restricted to basic boost pressure, other boost limiting functions prove to be operating normally, a modification to the wiring harness may be warranted. The affected wiring harness is located in the left hand door sill. This modification has been introduced into production as from VIN's K1004098 and K2001854.
Figure 1:
Wiring Harness Modification Procedure
1. Remove the scuff plate from the LH front door sill.
2. Release the clips over the wiring harness channel (Figure 1). Clip
off the cable tie at the front.
Figure 2:
For 1988 Models Only:
3. On 1988 models, the affected three wires are bundled into the main harness and must be separated out.
a. Pull up the harness and unwrap the electrical tape securing the harness.
b. Separate the three affected leads from the harness. The
lead for the ignition system
(green/white wire) and the
shielded coaxial knock detector cable (grey) are easily
identified. To identify the
ignition pulse lead (blue wire), trace the knock detector cable back to where it branches away from the main harness into its own sheathed harness. The blue wire that branches off the main harness into the sheath with the knock detector cable is the ignition pulse lead (Figure 2).
Figure 3:
c. Cut open an 80 cm (32 inch) length of PVC wiring sheath (source from your local jobber or stripped from an old
harness) and slide it over the blue and the green/white-leads. Slide the sheath as far forward and as far up as possible. Secure it with electrical tape (Figure 3).
d. Re-wrap the main harness with electrical tape.
Figure 4:
For 1989 Models Only:
4. On 1989 models, the affected three wires are already sheathed in their own harness alongside the main harness.
a. Slit the sheath the length of the door jamb channel and separate the coaxial cable from the blue and the green/white wires (Figure 4).
b. Wrap the sheath back around the blue and the green/white leads. Secure it with electrical tape.
Figure 5:
All Models:
5. Attach this "new" two wire harness along the knock detector cable
with electrical tape. Make sure
that the slit in the PVC sheath faces away from the knock detector cable.
6. Fit a new cable tie and refit the clips over the harness channel (Figure 5).
7. Refit the scuff plate.
8. Test the electrical functions and boost pressure.
Warranty Information
For warranty claims, use failure coding 37130-61-7-01-05. Labor time allowance is 0.3 hour which should be entered as straight time.