When you read the codes stored in an ECU you are hoping to find a "silver bullet".
These "bullets" tell you which part to replace or repair, however very few ECU's seem to be loaded with these. Instead the code is an indication of the problem area.
The actual fault still needs to be determined using diagnostic procedures.
Using EOBD the problem area is identified by the code, it then further divides the system into sub systems and finally components/specific operations.
P0420 for example;
P= Powertrain
0= Generic Code
4 = Emissions
20 = Catalyst efficiency below threshold
The prefix letter denotes the system
p = powertrain
B = body
C = Chassis
U = Network
The first number denotes the type of code
0 = Generic (all cars report the same code for a similar fault)
1 = Manufacturer specific ( this can differ from one model to another )
The second number identifies the subsystem
In powertrain;
1 = Fuel or Air
2 = Fuel or Air
3 = Missfire
4 = Emissions
5 = Vehicle or engine speed
6 = Control systems (ECU or output circuit)
7 = Transmission
8 = Transmission
9 = SAE reserved
0 = Fuel pressure control
The final two number numbers identify the setting variable.
Armed with this information it can sometimes help if you get "Blanks" these sound like a real bullets but are a long way short of being a silver bullet.
"unidentified fault codes"
No comments:
Post a Comment