Engine management system - MEMS (Diagnostics): Description and operation

Diagnostics

A diagnostic socket allows the exchange of information between the ECM and TestBook or a diagnostic tool using Keyword 2000 protocol.

The diagnostic socket is located in the passenger compartment fusebox which is located below the fascia on the driver’s side.

A dedicated diagnostic (ISO 9141 K Line) bus is connected between the ECM and the diagnostic socket and allows the retrieval of diagnostic information and the programming of certain functions using TestBook.

The ECM uses a ’P’ code diagnostic strategy and can record faults relating to the engine management and EM-CVT gearbox interface unit functions.

The ’P’ codes are qualified by one of the following failure types:

• Min - the minimum expected value has been exceeded
• Max - the maximum expected value has been exceeded
• Signal - the signal is not present
• Plaus - an implausible condition has been detected

From 2001 MY, after detecting a fault which causes an increase of emissions above the legislated threshold, in addition to storing a ’P’ code the ECM also illuminates a Malfunction Indicator Lamp (MIL) in the instrument pack. The ECM performs a 2 seconds bulb check of the MIL each time the ignition is switched on.

Diagnostic socket

Malfunction Indicator Lamp