GF07.16-P-3201GZ on-Board Diagnosis (OBD) Common Rail Diesel Injection - Function
GF07.16-P-3201GZ On-Board Diagnosis (OBD) Common Rail Diesel Injection - Function
- with CODE (494) USA version
The onboard diagnosis system (OBD) has the following tasks:
- Monitoring emission-relevant components and systems during driving
- Determining and storing malfunctions
- Display of malfunctions via the CHECK ENGINE indicator lamp
- Transferring determined faults in the workshop via a uniform interface to STAR DIAGNOSIS or to a standard read-out device
The following systems and functions are electronically monitored:
- Exhaust gas recirculation (EGR)
- Smooth running control (cylinders 1 to 6)
- Fuel system
- Glow system
- Intake air path
Readiness code
This code makes it possible to recognize that test procedures (function chains) relating to fault recognition have been completed. The readiness code detects the following electronic systems:
- Exhaust gas recirculation (EGR)
- Fuel system
- Smooth running control
The readiness code is set when 2 driving cycles, including a cold start, have taken place without error.
Warm-up cycle
Systems that are not constantly monitored are checked only when a warm-up cycle is executed.
A warm-up cycle consists of the following sub-cycles:
- Engine start
- Temperature increase > 4.5 °C
- Final temperature > 60 °C
- Engine switch-off
- Computer run-on for at least 10 seconds (wait for cooling fan run-on)
Driving cycle
One driving cycle consists of:
- Engine start
- 35 s at idle
- Engine switch-off
- Processor run-on (wait for cooling fan power down)
The CDI control unit checks its input and output signals for plausibility and recognizes possible faults.
Fault recognition
The following faults and error states are detected:
- Signals over or below the limit value (e.p. line open circuit, short circuit, defective sensor)
- Plausibility of signals
- Function chains with faults
- Error messages via the Controller Area Network (data bus/CAN bus) (CAN) from the fully integrated transmission control (VGS) control unit (Y3/8n4) for vehicles with transmission 722.9 and from the CDI control unit
Fault storage
The CDI control unit places recognized faults together with freeze frame data in its fault memory. If the fault is not confirmed during the following driving cycle, it is deleted. Emission-relevant faults are always entered, they have a high priority. Following 40 fault-free driving cycles, an exhaust gas relevant fault is deleted from the fault memory.
Consequential faults
If a faulty signal is detected and the corresponding fault code is stored, all the tests in which the signal is required as a comparative parameter, are ended. This ensures that no consequential faults are stored.
Fault freeze frame data and operating conditions
If a fault is detected, the following operating conditions to the fault code are stored as freeze frame data:
- Vehicle speed
- Engine speed
- Coolant temperature
- Charge air temperature
- Charge air pressure
- Engine load status
The CHECK ENGINE indicator lamp is actuated by Engine start from the CDI control unit. If there is no fault, the indicator lamp CHECK ENGINE goes out. If an exhaust-related fault occurs in 2 consecutive driving cycles, or limp-home mode is activated for the 2nd time, the CHECK ENGINE indicator lamp lights up. If there is a fault which can possibly damage the catalytic converters (TWCs) the CHECK ENGINE indicator lamp will flash. The CHECK ENGINE indicator lamp is switched off automatically by the CDI control unit after 3 or 4 consecutive fault-free driving cycles.
Read out the fault memory
Stored faults can be read out using STAR DIAGNOSIS or a standard reading-out device for "terminal 15 ON" or for "terminal 61 ON" via the data link connector.
Erasing the fault memory
Stored faults can be only be deleted using STAR DIAGNOSIS or a standard reading-out device for "terminal 15 ON".
The fault memory is not erased if the battery (G1) is disconnected.
CDI control unit power-down
After faults are erased, it is necessary to wait until the processor has completed its power-down sequence after circuit 15 is switched off. The processor power-down sequence lasts max. 10 s. If the cooling fan run-on is active, it is necessary to wait for the run-on time to complete.