This is what you do to read the codes from a BP26 and BPC8 ECUs. I have done it on my BP26 when I had one and it works great. I will make this into a sticky.
FIRST STEP: Make tester
Buy LED and appropriate resistor (red = 1kOhm, green/yellow/amber = 470 Ohm). Alternative is 12V dc packaged LED from electronics store.
Make up test lead so it follows this circuit (insulate all exposed wire, leaving the two contacts for the +B socket and the FEN socket, make sure you can see the LED from the drivers seat):
+B socket (12V)
--> Red wire (solder end of wire to make acceptable stiff end to stick in diagnostic socket)
--> Resistor (red = 1kOhm, green/yellow/amber = 470 Ohm)
--> LED - Longest leg of LED (positive)
--> LED - Shortest leg of LED (negative) Wire with stiff end (eg. paperclip)
--> FEN socket (diagnostics)
eg:
+B #------- Resistor -------*----------- LED ----*-------# FEN
(* = soldered join, # = solid end)
Use another insulated wire between TEN and GND on diagnostics socket. Ensure it cannot touch anything else.
SECOND STEP: Test ECU codes
1. Do above
2. Try/run engine
3. Turn off engine
4. Turn ignition back on
5. Observe LED
Car is OK then LED lights up like the dash lights e.g. for 4 seconds and then goes dark.
Fault code is one second light/ one second dark followed by 4 second intervals for a new fault code. e.g. Disconnect air mass flow meter, run car and you get 8 +1, disconnect timing pickup on camshaft and try and run car then you get 8 + 4+ 1 (codes are stored until you erase them).
6. To erase the codes - make sure you stereo etc is not code protected, then remove battery terminal for 30 seconds.
Note it is also possible to force the fuel pump (F/P), coolant fans (TFA) and have an electronic source for a timing device (IG-) from the diagnostic socket.
There is still the MEM tag -
Note on FEN to +B signal - this will only source 35.7mA maximum current drain so a normal 12V test bulb will not light. I was using the test bulb to drag the voltage up then measuring the voltage of
FEN, it would dip to 11.57V but the scan/refresh rate of my digital multimeter is about 0.5 second hence difficult to be certain of pulses. This practice is strictly dubious - hence the need for an LED
circuit or similar.
To know what the codes mean, read the GTR supplement of the 90-94 Mazda Familia FSM.
FIRST STEP: Make tester
Buy LED and appropriate resistor (red = 1kOhm, green/yellow/amber = 470 Ohm). Alternative is 12V dc packaged LED from electronics store.
Make up test lead so it follows this circuit (insulate all exposed wire, leaving the two contacts for the +B socket and the FEN socket, make sure you can see the LED from the drivers seat):
+B socket (12V)
--> Red wire (solder end of wire to make acceptable stiff end to stick in diagnostic socket)
--> Resistor (red = 1kOhm, green/yellow/amber = 470 Ohm)
--> LED - Longest leg of LED (positive)
--> LED - Shortest leg of LED (negative) Wire with stiff end (eg. paperclip)
--> FEN socket (diagnostics)
eg:
+B #------- Resistor -------*----------- LED ----*-------# FEN
(* = soldered join, # = solid end)
Use another insulated wire between TEN and GND on diagnostics socket. Ensure it cannot touch anything else.
SECOND STEP: Test ECU codes
1. Do above
2. Try/run engine
3. Turn off engine
4. Turn ignition back on
5. Observe LED
Car is OK then LED lights up like the dash lights e.g. for 4 seconds and then goes dark.
Fault code is one second light/ one second dark followed by 4 second intervals for a new fault code. e.g. Disconnect air mass flow meter, run car and you get 8 +1, disconnect timing pickup on camshaft and try and run car then you get 8 + 4+ 1 (codes are stored until you erase them).
6. To erase the codes - make sure you stereo etc is not code protected, then remove battery terminal for 30 seconds.
Note it is also possible to force the fuel pump (F/P), coolant fans (TFA) and have an electronic source for a timing device (IG-) from the diagnostic socket.
There is still the MEM tag -
Note on FEN to +B signal - this will only source 35.7mA maximum current drain so a normal 12V test bulb will not light. I was using the test bulb to drag the voltage up then measuring the voltage of
FEN, it would dip to 11.57V but the scan/refresh rate of my digital multimeter is about 0.5 second hence difficult to be certain of pulses. This practice is strictly dubious - hence the need for an LED
circuit or similar.
To know what the codes mean, read the GTR supplement of the 90-94 Mazda Familia FSM.
pm if interested
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