Connection Between Fiat Code Control Unit And Engine Control Unit - Fiat Brava Service Manual

Bravo-Brava Electrical system
Fiat CODE
55.
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KEY
CODE
WARNING
LIGHT
k
M a s t e r
< 2 s
0,7 s
< 1 0 s
Key 1
< 2 s
0,7 s
< 1 0 s
Key 2
< 2 s
0,7 s
< 1 0 s
M a s t e r
< 2 s
0,7 s
IGN.ON
w , I f i N D F F
^
ON
W , OFF
P4AO71L01
The diagram shows how the CODE warning light comes on depending on the key memorization
Key memorization with USED Fiat CODE control unit and UNUSED electronic fuel injec­
tion control unit
If the electronic fuel injection control unit has to be replaced, the Master Code inside it has to be memo­
rized.
To memorize the Master Code in the electronic fuel injection control unit, simply turn a key to the igni­
tion on (+15) position, after checking that the Fiat CODE control unit is working correctly.
Under no circumstances may electronic fuel injection control units be exchanged between cars
to check whether they are working.
During diagnosis, before replacing the electronic fuel injection control unit, make sure that the
component under examination really is faulty, because when the new electronic fuel injection
control unit is supplied, the Master Code will be memorized, rendering it entirely unusable on
other cars.
CONNECTION BETWEEN FIAT CODE CONTROL UNIT AND ENGINE CONTROL UNIT
The Fiat CODE control unit and engine control unit dialogue via a serial line consisting of a single cable.
The serial cable is of the bidirectional type; this means that the information travels in a sequential manner
from the engine control unit to the Fiat CODE control unit and vice versa.
The information exchanged between control units can relate to the following operating conditions:
A. Code check - whenever the key is turned to the ignition on position (even during starting), the en­
gine control unit, before starting engine management, requests the MASTER CODE from the Fiat
CODE control unit.
B. Code memorization - These operating stages concern the system when at least one control unit is
unused. The following cases may be distinguished:
- Unused engine control unit and Fiat CODE control unit.
- Used Fiat CODE control unit and unused engine control unit.
- Unused Fiat CODE control unit and used engine control unit.
Refer to the "Key Memorization" sub-section for the procedures to be adopted.
C. Sharing the serial line for diagnosis - Depending on the version, the connection between the Fiat
CODE control unit and the diagnostic socket may be configured as follows:
- For petrol versions with Bosch Monomotronic, IAW, Hitachi integrated fuel injection-ignition sys­
tem, the Fiat CODE system does not have its own diagnostic socket (Figure A next page). To
check the operation of the system, conduct a diagnosis on the engine control unit.
- For diesel versions with mechanical fuel injection pump, the Fiat CODE system has its own diag­
nostic socket.
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