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Range Rover P38 4-Wheel Traction Control Retrofit
V1.1 Instructions by Tamsin Rose, January 2022
tamsin.rose@outlook.com
IMPORTANT – PLEASE READ FIRST:
This upgrade involves in-depth modification to your vehicles braking system, improper installation
could cause undesired operation leading to serious injury or death. All electrical connections should
be made by a reliable means, Scotchlok style connectors are not acceptable for joining wires
together in a critical safety system– soldering with heatshrink tubing insulation or re-pinning the
connectors are preferred.
This guide assumes the reader some reasonable experience of working with the RR P38 vehicle and
the associated manuals.
The early type ABS modulators with 2-wheel or no TC have different internal configurations to the
later 4-wheel TC modulators and MUST NOT be paired with the late type ABS ECU, even though
they have similar connections. Similarly the late type modulator can not be installed without also
swapping the ABS ECU for the later type. Doing so will cause unpredictable operation of the
braking system.
The electrical manuals for both early and late type vehicles can be extremely helpful in diagnosing
any issues, however they both have some mistakes and inaccuracies.
Disconnect the vehicle battery prior to starting work, do not reconnect until all parts are installed
and complete.
Pay attention to routing when installing new wiring, it is preferable to follow the routing of the
existing wiring loom.
Fully read and understand all steps before commencing any modification. If you are in any doubt,
have a competent auto electrician carry out the modification.
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Parts Required:
Pre-99 Range Rover P38 without traction control or with 2-wheel traction control system
Post-99 ABS modulator block, part number SXC100000 or SXC100010. See Fig 01. Both
are almost identical, the 00010 superseded the 000000 during production. Manufactured by
Wabco. Some may have dates as early as 1998 printed on the data plate, but as long as the
part number matches they are suitable. IMPORTANT- although the pre-99 type ABS
modulators look almost identical they are different internally and will cause
unpredictable/dangerous functionality of the brake system if coupled with the Wabco D ABS
ECU. Pre-99 modulators with 2-wheel or no traction control have part numbers beginning
with STC or ANR.
Post-99 ABS ECU, part number SRD100500 or SRD1005001. See Fig 02. This is the
Wabco D ABS/TC ECU and is a black box with three connectors, in contrast with the early
type Wabco C ECUs which are a silver box with one large connector. A different version of
the Wabco D was also used on the Discovery 2 but these are not compatible.
Three electrical connectors that connect to the ABS ECU from a post-99 vehicle, with a few
inches of wiring loom attached. Connectors are C1584/C0504, C1586/C0505 and
C1585/C0506. Connector numbers differ depending on if the vehicle is LHD or RHD,
though the connectors themselves are the same. Henceforth referred to as C1584, C1586 and
C1585. See Fig 03.
ABS modulator electrical connector C1591/C0501 from a post-99 vehicle. Henceforth
referred to as C1591. This is the wiring loom multiplug connector that attaches to the ABS
modulator. Alternatively, additional pins and seals for the Econoseal J connector can be
purchased separately from RS, ebay, etc.
RR P38 RAVE workshop manual.
RR P38 Electrical Troubleshooting Manual (94-98 Model Years) – available in print and
online from many sources. Not essential, but useful.
RR P38 Electrical Troubleshooting Manual (99 Model Year onwards) – available in print
and online from many sources. Not essential, but useful.
Tools Required:
General toolkit, sockets, screwdrivers, wire cutters etc.
Soldering iron, solder, heatshrink tubing.
Electrical crimping tool, for Econoseal J connector pins.
Nanocom or other suitable diagnostic tool for troubleshooting (optional)
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Procedure
DISCONNECT BATTERY:
Disconnect the vehicle battery before starting work. Documentation for the Wabco D ECU suggests
that the unit can register unrecoverable faults if it is powered up with certain circuits disconnected,
though this has not been verified. However to prevent this possibility do no reconnect the vehicle
battery until all steps have been completed.
ABS Modulator Installation:
Remove or reposition the engine coolant reservoir to aid access to the modulator, as well as
for later routing of wiring.
Remove the existing brake modulator/master cylinder unit as per the workshop manual
instructions, and install the new modulator. Do not power up the vehicle or attempt to bleed
the brake system until after the new ABS ECU is also installed. Check the brake switch is
properly attached to the pedal and functioning correctly.
Modify the wiring loom electrical multiplug by adding a pin to position 3 and route a (black)
wire from it back to the passenger footwell. See Fig 04. Either transplant this pin from a
spare electrical connector from a donor vehicle, or purchase new pins to add into the
connector. Ensure appropriate wire seals for the Econseal J connector are used.
Reconnect the multiplug and single pin ground connector to the ABS Modulator
ABS ECU Installation:
The ABS ECU is located in the passenger footwell, remove the glovebox and nearby trim
panels to aid access. See Fig 05.
Remove the Wabco C ABS ECU (silver box) and disconnect it’s large electrical connector.
Free up some of the wiring loom by clipping off any cable ties etc to make it easier to work
on
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Wiring Modifications:
Remove the back cover from the ABS ECU multiplug to make it easier to view the wire to
pin assignments.
Do not cut all the wires yet or you may struggle to reconnect them to the right pins!
Remove wires one by one from the Wabco C multiplug and join them to the appropriate pin
of the appropriate connector for the Wabco D ECU. Most are colour to identical colour, but
be careful as there are some duplicate colours. Also the Wheel speed sensor wires where
found to all be black or brown on the test vehicle, despite the wiring manual stating they
should all be colour coded. Take your time and match the pinouts as per the tables at the end
of this document. See Fig 06.
Some wires will be left unused (light green for diagnostic socket for example). Cut them and
seal up the ends with heatshrink tubing.
Connect the black wire added from the modulator multiplug to pin 3 of C1585.
Run two wires to from the ABS ECU to the bottom of the engine bay fuse box. Use them to
join pin 8 of C1584 into the wire of pin 8 of C177, and pin 9 of C1584 into the wire of pin 7
of C177.
Modify the funtion of Relay 2 in the engine compartment fuse box – either remove it and
short the output terminals using a jumper wire, or connect the Black/Green wire left over
from pin 8 of the Wabco C multiplug to ignition live using an appropriate gauge wire. This
is because the main power supply layout differs between Pre/Post 99 vehicles, the early
models are fed via a fusebox relay however the late type should be permanently powered on
this pin. See electrical manuals for details if required.
Finishing up:
Double check all connections are sound.
Mount the Wabco D ECU securely behind the glovebox, some bracket fabrication may be
required. See Fig 07.
Fill the modulator reservoir with brake fluid.
Reconnect the battery, switch on the ignition – the abs and traction warning lights should
come on and the ABS pump should start running. Switch off the ignition after a few seconds
if all seems well. If the traction control warning does not illuminate then a bulb will need
installing, or replacing, in the back of the instrument cluster.
Depressurise the brake system and bleed the entire brake system as per the procedure in the
workshop manual. Do this exactly as written, do not skip any steps.
After bleeding the brakes power up the vehicle, wait for the ABS pump to stop running, start
the engine and drive off slowly – the warning lights should go off after approximately
reaching 5mph as is normal for the P38.
You can test the new TC system by driving over a loose traction surface and applying the
accelerator – the brake modulator should be heard to click audibly and the TC light on the
instrument cluster will illuminate for a few seconds.
If all works ok then congratulations, you just installed 4-wheel traction control into your P38
Range Rover!
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Fig 01- SXC10000 ABS Modulator
Fig 02- SRD1005001 ABS ECU
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Fig 03- Connectors with wire tails
Fig 04- ABS modulator Multiplug
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Fig 05- Early ABS ECU removal
Fig 06- Wire Splicing
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Fig 06 – New ABS ECU mounted