| Electronics |
| Fault Codes: The Bosch ECU's have a facility to store information about any fault which may have occured. These faults can be read from the ECU without much difficulty. The term "Fault Code" refers to a coded number which is given to the engineer via the ECU dashboard light flashing. The ECU can be set to "Test Mode" by shorting pins A and B of the blue diagnostic plug. you can buy a special piece of equipment for about £25 to do this, but it's just a switch and two wires! it can be done for free by using a piece of thin copper wire or a paper clip! The numbers come out in a sequence but are repeated three times incase of human error. For example, if the fault was number 35 (idle speed control valve) the light would flash this sequence: OOO / OOOOO / OOO / OOOOO / OOO / OOOOO ...repeated 3 times 3 5 3 5 3 5 OK, now we've grasped how to understand the sequences, it gets a little more complicated... The ECU recognises it's in "Test mode" by outputting the number 12 three times. Then it outputs the fault three times, followed by 12 three times. If there is just one fault, this will loop continually... But if there is a second fault it will show up too, but seperated by the 12's. For just fault 35: 12 12 12 / 35 35 35 / 12 12 12 / 35 35 35 / 12 12 12 etc... For faults 35 and 14 (coolant temp sensor): 12 12 12 / 35 35 35 / 12 12 12 / 14 14 14 / 12 12 12 / 35 35 35 / 12 12 12 / 14 14 14 etc... |
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| Code Chart: I have found differing versions of the Fault Codes on the net, so I've compiled my own version to bridge some gaps, and sort out some mistakes. Download in MS Word format, CLICK HERE! To view the online version, CLICK HERE! |
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| ECU Connector: Info for M2.7, but is still the same for M2.5 just with with fewer bits! This is a list of the pins and what they connect to, it helps when checking signals and breaks in wiring. The referances relate to the wiring diagram, further down the page. |
| Ter. 1 Final stage, ignition module K 20/Ter. 4 Ter. 2 Recognition 1 at gear S 53 Ter. 3 Ground actuation for fuel pump relay K 68 / Ter. 85 B Ter. 4 Ground actuation for idle speed adjuster M 33 Ter. 5 Ground actuation for tank vent valve Y 34 Ter. 6 Unoccupied Ter. 7 Signal, hot wire mass air flow meter P 44/Ter. 3 Ter. 8 Signal, Hall sensor cylinder recognition P 47/Ter. 2 Ter. 9 Signal, odometer frequency sensor P 21 Ter. 10 Ground Ter. 31 Ter. 11 Signal, knock sensor Ter. 12 Voltage supply, Hall sensor P 47/Ter. 3; throttle valve potentiometer P 34/Ter. 1 Ter. 13 Diagnostic excitation lead, diagnostic plug X 1 3/Ter. B Ter. 14 Ground Ter. 31 Ter. 15 Unoccupied Ter. 16 Ground actuation for injection valve Y 7, cylinder 3 Ter. 17 Ground actuation for injection valve Y 7, cylinder 1 Ter. 18 Battery Ter. 30 Ter. 19 Ground Ter. 31 Ter. 20 Unoccupied Ter. 21 Ground actuation for charge pressure bypass valve Y 12 Ter. 22 Ground actuation for engine telltale Ter. 23 Unoccupied Ter. 24 Ground Ter. 31 Ter. 25 Ground actuation for hot wire mass air flow meter P 44 / Ter. 4, 'burn off' signal Ter. 26 Ground, hot wire mass air flow meter P 44/Ter. 2 Ter. 27 Battery Ter. 1 5 Ter. 28 Signal, oxygen sensor P 32 Ter. 29 Unoccupied |
| Ter. 30 Ground supply for: knock sensor P 46 coolant temperature sensor P 12 intake air temperature sensor P 29 throttle valve potentiometer P 34 Ter. 31 Ground actuation for hot start valve Ter. 32 Tj signal for hoard computer Ter. 33 Unoccupied Ter. 34 Ground actuation for injection valve Y 7, cylinder 2 Ter. 35 Ground actuation for injection valve Y 7, cylinder 4 Ter. 36 Ground actuation for fuel pump relay K 68/Ter. 85 Ter. 37 Voltage supply for: control unit K 61 hot wire mass air flow meter P 44/Ter. 5 Ter. 38 Unoccupied Ter. 39 Unoccupied Ter. 40 Input signal, air conditioning compressor Ter. 41 Input switch, air conditioning ready Ter. 42 Ground Ter. 31 Ter. 43 Tachometer Ter. 44 Signal, Intake air temperature sensor P 29 Ter. 45 Signal, coolant temperature sensor P 12 Ter. 46 Unoccupied Ter. 47 Unoccupied Ter. 48 Signal, inductive pulse pick up P 35/Ter. 2 Ter. 49 Ground, inductive pulse pick up P 35/Ter. 1 Ter. 50 Unoccupied Ter. 51 Unoccupied Ter. 52 Recognition reverse gear Ter. 53 Signal, throttle valve potentiometer P 34/Ter. 3 Ter. 54 Unoccupied Ter. 55 Bi directional data lead, diagnostic plug X 13/Ter. 6 |
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| Engine Wiring Diagram: M2.7 shown, but M2.5 is the same - minus some of the turbo related items. |
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