Scan Tool Testing and Procedures

TestBook/T4 Diagnostics

the ECM stores faults as Diagnostic Trouble Codes (DTC), referred to as 'P' codes. the 'P' codes are defined by OBD legislation and together with their associated environmental and freeze frame data can be read using a third party scan tool or TestBook/T4. TestBook/T4 can also read real time data from each sensor, the adaptive values currently being employed and the current fuelling, ignition and idle settings.

Several different drive cycles are defined by OBD legislation for fault diagnosis. Each drive cycle is a precise routine which the engine or vehicle must undergo to produce the conditions that enable the ECM to perform diagnostic routines. TestBook/T4 can be used to view the status and results of the diagnostic routines performed by the ECM. When a fault code is stored, it will indicate, via TestBook/T4, the drive cycle required to verify a repair.

the ECM only records a fault after it has occurred on more than one drive cycle.This fault strategy is referred to as debouncing. When it is first detected a fault is stored as a temporary fault. If the fault recurs within the next 40 warm-up cycles, the fault is stored as a permanent fault and freeze frame data for the second occurrence is recorded. If the fault does not recur within the next 40 warm-up cycles, the ECM deletes the temporary fault from memory.

the ECM illuminates the MIL when requested to do so by the EAT ECU, to perform a bulb check when the ignition is switched on and for any emissions related fault. There is no MIL illumination for non emission related engine management faults.

Resetting the adaptions will clear all adaptions from the ECM memory.