Subject: Reading BMW Fuel Injection Fault Codes Author: shogun (moderator) : member since March, 2004 : 12553 posts Posted on: 2008-12-23 22:18:20

All BMWs from 1984 use a sophisticated Bosch engine management system called Motronic. The Motronic system (also called the Digital Motor Electronics or DME) is hands down the best overall fuel injection system that you can use when you consider price and performance. Ignition timing and fuel delivery are all controlled by a digital map that is recorded in a removable chip within the main fuel injection (DME) computer. The computer takes input from a variety of sensors that are located on the engine – cylinder head temperature, altitude (ambient air pressure), crank angle, throttle position, exhaust gas oxygen (mixture), ambient air temperature, and mass air flow. The DME chip is programmed from the factory with certain performance characteristics (mostly conservative) so that the engine will react well under a host of varying conditions.
As with any electronic device, components can fail, triggering problems with the system. The BMW Motronic system is designed to react to these failures and indicate them to the driver, so that they can be fixed. If one of the computer's sensors is not working properly, then the computer may not be able to successfully identify the current state of the engine and choose the appropriate fuel mixture or timing advance level. When this happens, the fuel mileage drops, engine performance suffers, emissions increase, and the car typically illuminates the 'check engine' light.

In order to accurately find the sensor and fix the problem, you will need to find out which error code is being triggered by the computer. Pre-1995 BMWs were equipped with what is known as OBD I (On Board Diagnostics Level I). Stating in 1996, they were equipped with a more advanced version called OBD II, which was mandated by the US government, in order to standardize automotive repair and diagnostics. The OBD system is responsible for monitoring and checking all of the fuel injection sensors and systems in the vehicle, and turns on the 'check engine' lamp if it finds a problem or irregularity with one of them. The computer lodges a Diagnostic Trouble Code (DTC) in the main computer until it is read and reset. Disconnecting the battery does not reset the codes - they need to be manually reset.

For BMWs equipped with OBD I, you can read the codes using a system that is built into the car. For OBD II compliant cars (1996 and later), the codes can only be read using a scan tool (more on this later).

To read codes for an OBD I car, you start by turning the ignition key on (do not start the engine) and pressing the gas pedal to the floor five times within a period of five seconds. If you proceeded correctly, then the check engine lamp will light on for five seconds, then blink off, then blink on for 2.5 seconds, and then go off for another 2.5 seconds. After this, the computer will start to show you the trouble fault codes that are stored.

The codes are given by short flashes of the check engine light, followed by short pauses. The codes are all four digit numbers. For example, the trouble fault code for monitoring the battery voltage level is 1231. This would show up flashing as "flash - pause - flash - flash - pause - flash - flash - flash - pause - flash." I suggest having a pen and paper handy when you do this, as the codes have a tendency to flash faster than you would think.

If there is more than one fault code stored, then each code will be separated by a 2.5 second pause. When there are no more codes to be read, the computer will give the code 1000, which is one short flash, and then the light will remain off. Then the check engine light will flash a half-second and then turn off. To read the codes again, simply turn the ignition key off and on again and repeat the procedure with the gas pedal (five times within five seconds).

Here is a table that represents all of the possibly fault codes that can be read using this method:
http://www.pelicanparts.com/bmw/techarticles/Mult-Code_Reading/Mult-Code_Reading.htm
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Reading Engine Fault Codes

To the best of my knowledge only US spec E34s are equipped with the feature to read engine codes as described below. Apparently the ability the access codes was a US EPA requirement on new cars built after 19XX. Canadian E34s might very well have this feature too.

Fault codes can be read by turning the ignition key on and fully depressing the accelerator pedal to the floor five times in five seconds. The Check
Engine Light will then remain on for five seconds, blink off, come on for 2.5 seconds, then go off for 2.5 seconds. At this point, the fault codes
will begin to flash.

If more than one fault has been detected, each code will be separated by a 2.5 second pause. When all the fault codes have been displayed, there will
be a 0.5 second flash and then the light will remain off. To read the codes again, turn the ignition key off and then on again. Depress the accelerator
pedal to the floor five times quickly (within 5 seconds). The codes will begin to repeat.

To erase the fault code memory, first make sure that the fault code 1000 (short blink and light goes out for a long period) is present, then depress
the throttle fully for at least 10 seconds. Reactivate the fault code memory as described earlier and check for the 1444 code (no faults stored).

Here are the codes (from Bentley):

1211: DME Control Module
1215: Mass Air Flow
1216: Throttle potentiometer
1218: Output Stage Group 1
1219: Output Stage Group 2
1221: O2 Sensor 1
1212: O2 Sensor 2
1222: O2 lean/rich control stop
1213: O2 sensor 2 lean/rich c/s
1223: Coolant Temp Sensor
1224: Air Temp Sensor
1225: Knock sensor 1
1226: Knock Sensor 2
1227: Knock Sensor 3
1228: Knock Sensor 4
1231: Battery Voltage Monitor
1232: Idle Position Signal
1233: Wide Open Throttle Signal
1234: Speedometer A signal
1237: A/C cut-off
1242: A/C signal
1243: Crankshaft Position Sensor
1244: Camshaft Position Sensor
1245: Elect. Tranny control intervention
1247: Ignition Secondary Monitor
1251: Fuel injectors 1,3,5
1252: Fuel injectors 2,4,6
1251: Fuel Injector 1
1252: Fuel Injector 2
1253: Fuel Injector 3
1254: Fuel Injector 4
1255: Fuel Injector 5
1256: Fuel Injector 6
1257: Fuel Injector 7
1258: Fuel Injector 8
1261: Fuel Pump
1262: Idle Speed Control
1263: Evap. System
1264: O2 Sensor Heater
1265: Check Engine Lamp
1266: VANOS
1267: Air Pump
1271: Ignition Coil 1

1272: Ignition Coil 2
1273: Ignition Coil 3
1274: Ignition Coil 4
1275: Ignition Coil 5
1276: Ignition Coil 6
1277: Ignition Coil 7
1278: Ignition Coil 8
1281: DME Memory
1282: Fault Code Memory
1283: Fuel Injector Output Stage
1286: Knock Control test pulse
1000: End of faults
1444: No faults

source: http://www.bmw4life.com/stompTest.htm

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• Reading BMW Fuel Injection Fault Codes (url) - shogun 2008-12-23 22:18:20 (190 views)