Fault of the Looms
Several owners have reported experiencing repeated malfunctions of the gearbox -
even after having the gearbox and Torque Converter replaced. They
have taken it to
a main dealer or an autobox repair specialist - only to be told
that no faults were present. The following pages are an explanation of the connections
throughout the engine management and automatic gearbox looms to enable the owner
to carry out his own continuity/fault checks.
Slippage - No error codes
In cases of slippage, that the revs of the engine rise at the same road speed,
as if it were a manual gearbox clutch slipping - it is worth checking the MAF.
The Mass Airflow Sensor is mounted in the air inlet trunking between the air
filter and the inlet manifold. If you check out the page dealing with the
EECV, this reports that
symptoms for a fault with the MAF are : Incorrect gearshift scheduling – torque
converter clutch engages/disengages early/late. The
Comprehensive Component Monitor checks the MAF
constantly but sometimes no error codes will be
generated if the readings are just under the fault parameters. The torque converter clutch is exactly what
makes the gearbox feel that it is slipping - it is because the clutch lock-up
has not occurred when it should.
It is fairly simple to remove the housing from the air filter box and the inlet
hose, disconnecting it and removing it to the bench. NOTE: Use care with the
sensor - it is fragile so do not drop it or submit it to sudden shocks.
See Clean MAF
NOTE: One owner, Oliver, reports that this
has cured his symptom of torque converter slip or loss of 4th gear (overdrive).
Pete C has also reported that his gearbox was just staring to slip again, (after
replacing gearbox and TC last year) and his MAF was filthy. Carb cleaner brought
the interior up to a shine again and the slipping stopped immediately.
In some circumstances the MAF can be faulty but does not fail
the CCM checks. A Test is available to check for this
and this is based on the latest Ford advice.
the Speedometer is erratic and the automatic gearbox is behaving strangely then
suspect the Vehicle Speed Sensor (VSS). If this is faulty or its
connection is poor then it will have a marked effect on gearbox operation, and
OBD will report DTCs for this device. Check the connection to the
and replace as necessary.
Now we come to the more serious symptoms - O/D light flashing, delayed/harsh
gearchanges, incorrect gearchanges. Fault codes may include errors with Solenoid
C (or #3, depending on tester). Experience has shown that
Loom faults often cause different codes that come and go. While some codes
clear, others are created and this is a good indicator - a genuine fault would
remain until repaired. Codes which appear after heavy rain or washing the car
may also lead one to suspect the wiring - but bear in mind the Battery Cover
We know from the Revisions page that 24V engines after
01/04/95 had protective sheathing, and that 16V engines suffered from the engine
looms chafing on the corner of the cylinder head. One owner experienced a leak
which trashed his 24V wiring loom over a period of 2 years and diagnostics
remained a puzzle for some time - even using state of the art equipment - until
the reason for the gearbox problems was discovered:
Extended research by FordScorpio.co.uk has traced the problem to faulty Arnitel
wiring, used in the engine bay until June 1996, after which production changed
to Raychem44 wire, which has proved to be safe. Even so, the Arnitel wire has
proved to be reliable on most Scorpio vehicles, just a tiny unlucky minority (9
owners so far) suffering from faulty looms. This should not be confused with
another wiring problem for the fuel cut off loom on
DOHC models, which caused some confusion until this was recognised as a separate
issue effecting all DOHC Scorpios..
But how can we tell if a wiring loom is causing problems rather than a physical
fault inside the gearbox? This needs a detailed knowledge of the colour codes of
the wires, the locations of the connectors and all of the pins inside them.
Impossible? Not for fordscorpio.co.uk !!
First, we need to know the physical attributes of the loom. We need to
understand where it runs from the gearbox to the engine bay and to the EECV.
The picture on the right shows the loom on the top of the A4LDE. In this case
the engine is a 24V, but the path is the same. The loom makes two connections to
the A4LDE gearbox through two multiplugs, then runs up over the bell housing and
thence into the engine bay. The loom is then joined by other connections for the
engine sensors (ECT, IAT, TPS, CKP and the HO2S sensors, among others) and then
runs from the (facing front of the car) right hand side of the engine to the
engine bulkhead, where it terminates in a large square connector beneath the ABS
The picture on the right shows this connector, complete with the square nut to
clamp it up tight and prevent the entrance of moisture.
The loom on the other side of this connector travels around the bulkhead and
enters the cabin through a large grommet, running straight to a large connector
on the EECV.
On the face of it, it may seem impossible to trace every pin and track it back
inside this loom bristling with wires through the twists and turns in the
bulkhead. In fact, testing the whole loom should be quite straightforward.
1. Note that there is no physical break in the loom between the connector C402
on the EECV (from now on, called by it's correct abbreviation, PCM) and the
square connector on the engine bulkhead. (C112 and C110)
2. There is no physical break in the loom between the large square connectors
C112 or C110 on the engine bulkhead to the connector C604 on the A4LDE,
hereafter called by it's correct abbreviation Transmission Hardware Unit (THU)
3. A wire is coloured the same in the entire loom from the connection on the PCM
(C402) to the multiplug on the THU (C604)
4. Wires connecting sensors which operate at low signal voltages are coated in
gold and protected by a special grease which does not contain lithium (which
would lift the gold plating and cause problems) So if you open a connection and
there are some gold and some tin connections, you will know that the gold ones
are critical signal wires.
5. A simple circuit test is insufficient for this diagnostic - it is not
sensitive enough to detect voltage drop and leakage across wires. A digital
multimeter is essential for this task. They may be obtained quite cheaply from
If follows that, since a pin in the PCM connector C402 has no physical break
between that and the bulkhead connector C112, we can make continuity checks
between the corresponding pins. Leakage checks would also be useful - connect to
one pin on C402 and check all the pins in C112 - if a voltage is detected on a
pin other than the correct one this would indicate a break in insulation. This
can either be investigated further and repaired (knowing which colour wire to
look for inside the loom) or by replacing the loom altogether. Similarly, the
engine loom can be checked between the bulkhead connector C402 and the THU
Using the data very kindly supplied by Ford (Europe) I have prepared tables of
connections at each point: C402, C112, and C604 and the corresponding colour
code and usage of the wire. Since several owners of 16V cars have experienced
doubts about their loom integrity, I have started with their coding. Others will
follow, and will have their own pages selected from the menu on the left.
Gaining access to the connections
So where are they?
©. Ford (Europe)
The PCM is behind the glove box. This is removed by pressing out the supports
and lowering the glove box. Remove under trim fasteners and remove the under
trim panel. The PCM is the larger unit secured into the bulkhead with rivets.
The PCM connector C402 can be unbolted and pulled away from the PCM.
C112 and C110
©. Ford (Europe)
The bulkhead connector C112 is, as already stated, on the left hand engine side
bulkhead beneath the ABS module. The single bolt through the top is released and
the halves of the connector separated. Bear in mind that when the two faces are
upward they are mirror images of each other - the top two holes on the lower
half are 21 and 27, while pins on the upper half are 27 and 21. Some models have
two connectors, the second being identical in pin configuration, and is called
C110. Most gearbox functions pass through C112, and engine wires through C110.
©. Ford (Europe)
The HTU multiplug C604 is mounted on the right hand side of the gearbox just
forward of the transmission selector fulcrum. It may be reached if there is
enough room for an arm - but remember that if the connector is pulled off it
will need to be replaced and this should be borne in mind. Two locking lugs need
to be released at the same time that the multiplug is pulled free. DO NOT pull
on the wire - this may result in dislodging the terminals inside. In the event
that some terminals are showing corrosion, these can be repaired using a repair
kit available from a Ford Main Dealer. If a terminal is gold-plated, it must be
repaired using another gold terminal and lithium based greased must not be used.
The repair kit contains the correct special grease. This grease is Myogel 760A
Finis 5 030 186.
It may be necessary to lower the gearbox slightly, and on some models (24V
especially) the exhaust may need to be removed first. I suggest that the whole
operation will be much easier with two operators, one at each end to enable the
tests to be carried out efficiently.
Complete wiring details for the Scorpio in Acrobat form are
shown here -
note: this link takes you away from www.fordscorpio.co.uk.
Now use the links on the left corresponding to your engine - and good luck!