Page 19.16 Fault code table (Citroen and Peugeot)
11 End of diagnosis
12 Initiation of diagnosis
22 Stepper motor
31x Lambda control
42 Injector or fuel pump control
52 Lambda control
53x Battery voltage
x Faults that typically will cause the ECM (Electronic Control
Module) to enter LOS (limited operating strategy) and use a default
value in place of the sensor.
To obtain fault codes short the green lead side of the Fault Code
Reader (FCR) multi-plug to earth for 4 seconds with the ignition on
while an assistant watches the fault lamp on the dashboard (or use two
long lengths of cable). To clear the fault codes short for 10 seconds,
or remove the ECM multi-plug. The FCR is situated by the o/s headlamp.
My 1994 Citroen AX had a running problem. The ECM was unable to read
the Coolant Temperature Sensor (CTS) giving fault code 14. The CTS was
replaced to no avail. The replacement died two years later. The sensor
should read around 4k ohm at 10C, 2.2 - 2.8 k ohm at 20 C. It will go
open circuit if the thermistor is dead. To change the CTS place a 19mm
socket over the sensor before partially inserting a 1/2" drive. Placing
the socket over the sensor with the drive fully inserted will break the
sensor from its mounting.
Fault code 14 makes the ECM substitute a default value which makes the
engine run badly. The problem was a poor connection on pin 25 of the
multi-plug (P19.14 - the lead in the illustration is on the wrong end
of the plug). The middle row starts at pin 20 from the lead end. (Check
for continuity between pin 25 and the CTS first.) Removing and
replacing the plug would cure the problem and remove the fault code
temporarily. I eventually cured the problem by cutting the lead to pin
25 and making a permanent connection to the male pin on the ECM. This
was done by cutting a 2 amp female spade connector and sliding it
completely over pin 25. The lead was then soldered to the spade
connector which gave a better joint than soldering directly to the pin.
The lead should face away from the multi-plug so it is not crushed when
the plug is replaced. I also had to connect one side of the CTS to the
earth point on the suspension strut upper mounting, as both the earth
and 5V signals were intermittent due to corrosion on the ECM
If the Throttle Potentiometer (TPS) wears out (mine did at 50,000), a
replacement is around 300 quid (Citroen parts are around 25% cheaper in
France). The manufacturing cost is probably no more than a pound. I
wrote to the Consumers Association but they weren't interested. If
you're buying second hand check the fault codes. Take the vehicle for a
run first in case the owner has cleared the fault codes from the memory
of the ECM!
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