Dtc Memory/Troubleshooting; Troubleshooting Aids; Combined Plug Connections - Distinguishing Between Wires - Porsche 928 Workshop Manual

39
Differential,
transaxle system
928
DTC memory / Troubleshooting
Important notes
If warning displays light up and/or faults are
shown in the DTC memory of the PSD/ABS,
they may also have been triggered by the fol-
lowing problems:
- Control unit supply voltage less than 9.5
Volt (undervottage)
- Control unit plug disconnected.
- Contact resistance caused by poor
ground connections. leading to differen-
ces in potential or inadequate shielding of
speed sensors. The poor ground connec-
tion may not only occur at the affected
components, but also at other important
grounding points.
- ImpottankThe warning "PSD off'
may ap
pear in the display fields of the instrument
cluster, even though no fault is stored in
the DTC memory. Check the lock hydrau-
lics (lock operation) in this case (as of
Page D39-247).
Troubleshooting aids
When measuring with the multimeter at the
control-unit plug, make up 1 or 2 auxiliary
leads in your own workshop, each with 2 flat
pin plugs No. 17.457.2, to avoid damaging
the plug contacts in the control-unit plug du-
ring the test.
Combined plug connections - distinguish-
ing between wires
In the brake pad wear, speed sensor and HF
sending unit wiring there are several com-
bined plug connections of similar pattern. In
this area, the wires can be distinguished as
follows:
- Shielded wires for the speed sensors and
HF sending units.
- 2 wires with a protective tube for brake
pad wear.
- One pin and one socket exist on the HF
sending unit plug connections. The speed
sensor plug connections possess 2 pins
as well as 2 sockets on the opposite side.
- Two combination connectors are located
one above the other in the spare tire
area. The wires are identified there with
L
= rear lefl and
R
= rear right.
D39 - 228
PSD diagnosis/Troubleshooting
Printed in Germany XXXV. IDS6
l