CHECK ENGINE LIGHT
CHECK ENGINE or Malfunction Indicator Light (MIL) is illuminated when any of the following occur
Scheme 74
- Completion of the next consecutive driving cycle where the previously faulted system is monitored again and the emissions relevant fault is again present. (Scheme 74)
- Immediately if a catalyst damaging fault occurs.
- A malfunction of a component that can affect the emission performance of the vehicle occurs and causes emissions to exceed 1.5 times the standard.
- Manufacturer-defined specifications are exceeded.
- An implausible input signal is generated.
- Catalyst deterioration causes HC-emissions to exceed a limit equivalent to 1.5 times the standard.
- Misfire faults occur.
- A leak is detected in the evaporative system.
- The oxygen sensors observe no purge flow from the purge valve/evaporative system.
- Engine control module fails to enter closed-loop operation within a specified time interval.
- Engine control or automatic transmission control enters a limp home operating mode.
- Key is in the ignition on position before cranking (Bulb Check Function).
MoDiC System
The BMW MoDiC diagnostic system was developed to meet the diagnostic needs of BMW vehicles. It compliments the DIS tester as a diagnostic tool that enables the technician to quickly troubleshoot electronic faults and problems with the vehicles. The advantage of the MoDiC is its mobility. The tester can go anywhere in the workshop and to the vehicle. It can remain connected to the vehicle while it is driven to check for intermittent problems or conditions that only occur while the vehicle is driven. The MoDiC is a personal computer with interchangeable batteries, UNIX operating system, 3 gigabyte hard drive for data/program storage, 32 MB working memory, 90 megahertz Pentium processor, Diagnosis Information System (DIS), Technical Information System (TIS), Digital Multimeter, Counter, and single channel oscilloscope. Objectives used in the development of the MoDiC included maximum functional efficiency and mobility in the workshop, diagnostic procedures similar to the DIS, operation similar to the DIS, basic measurement techniques available, integrated TIS function, common software CD for both the MoDiC and DIS.
DIS Plus
BMW DIS Plus diagnostic system features a comprehensive multimeter system (including an oscilloscope) that is used to perform various tests and measurement during the diagnosis and troubleshooting procedures. Also included is the Technical Information System (TIS). TIS is the same system that operates through dealer main computer system.
Group Tester One (GT-1)
GT-1 replaces the MoDiC series of portable diagnostic tools. It has the same processor as the DISplus. Other features include a DVD ROM drive, TFT color display, integrated PCMCIA card reader, integrated chip card reader, touch screen (same as DISplus), workshop grade case, ASM-technology motherboard, temperature operating range from 35°F to 105°F, 2.5 hours of operation with a fully charged battery, and can be powered by vehicle battery.
A diagnostic cable is used to connect diagnostic head to a vehicle with the 20 pin underhood connector. Cable consists of 20 pin connector, cable and 21-pin plug for connection to the head. An OBD-II diagnostic cable is used to connect diagnostic head to OBD-II diagnostic connector.
Hard & Intermittent Failures
A fault code is stored within the respective control module upon first occurrence of a fault in system being checked. CHECK ENGINE light will not be illuminated until completion of second consecutive driving cycle where previously faulted system is again monitored and a fault is still present or a catalyst damaging fault has occurred. If second drive cycle was not complete and specific function was not checked, PCM counts third drive cycle as next consecutive drive cycle. CHECK ENGINE light is illuminated if function is checked and fault is still present.
If an intermittent fault is present, and it does not cause a fault to be set through multiple drive cycles, 2 complete consecutive drive cycles with fault present are required for CHECK ENGINE light to be illuminated. Once CHECK ENGINE light is illuminated it will remain on unless specific function has been checked without fault through 3 complete consecutive drive cycles.
Fault code will also be cleared from memory automatically if specific function is checked through 40 consecutive drive cycles without fault being detected or with use of DIS Plus or GT-1 scan tool. To clear a catalyst damaging fault from memory, condition under which fault occurred must be evaluated for 80 consecutive cycles without fault reoccurring.
Readiness Code
Readiness code provides status (yes/no) of the system having completed all required monitoring functions or not. The readiness code is displayed with an aftermarket Scan Tool or the DISplus/MoDIC/GT-1. The code is a binary (1/0) indicating the following
- 0 = Test not completed or not applicable - 6 cylinder vehicles (not ready - V8 and V12)
- 1 = Test completed - 6 cylinder vehicles (ready - V8 and V12)
A readiness code must be stored after any clearing of fault memory or disconnection of PCM. A readiness code of "0" will be stored after a complete diagnostic check of all components/systems (that can turn on Malfunction Indicator Light) is performed. Readiness code was established to prevent anyone with an emissions related fault and a Malfunction Indicator Light on from disconnecting battery or clearing fault memory to manipulate results of emissions test procedure. Complete readiness code is equal to one byte (8 bits). Every bit represents one complete test and is displayed by scan tool
- 0 = EGR monitoring (= 0, N/A with BMW)
- 1 = Oxygen sensor heater monitoring
- 1 = Oxygen sensor monitoring
- 0 = Air condition (= 0, N/A with BMW)
- 1 = Secondary air delivery monitoring
- 1 = Evaporative system monitoring
- 0 = Catalyst heating
- 1 = Catalyst efficiency monitoring
Drive vehicle in such a manner that all tests listed above can be completed. When complete readiness code equals "1" (ready) then all tests have been completed and system has established its readiness.
Readiness code can be checked with DISplus/MoDIC/GT-1. This is helpful in verifying that drive cycle criteria was achieved. A repair can be confirmed before returning vehicle to customer by a successfully completed drive cycle. See .
DRIVE CYCLES
For drive cycle (Scheme 74)
SUMMARY
If no hard DTCs are present, driveability symptoms exist or intermittent DTCs exist, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnosis procedures.