Engine Management Test:

When an engine management system fault occurs the instrument pack will display a "CHECK ENGINE" warning. The EMS ECU will store a code that identifies which circuit contains the fault and can be read using one of two methods:

^ Instrument Pack:

Switch off the ignition key and wait 5 seconds. Turn the ignition key on and press the VCM button. If more than one fault exists, only the highest priority fault code will be displayed by the instrument pack. A list of fault codes can be found in the XJ6 Service Manual, Book 2, page 18-11.


NOTE: JDS should not be used for an engine management test until the mechanical, fuel, cooling, and secondary ignition systems are operating correctly. For diagnostic information, refer to the XJ6 Service Manual, Book 2, pages 12-10 - 12-15.



^ JDS:

During an engine management test, JDS will request that pod 7 be connected to enable communication with the ECU. JDS will then request that pod 1 be connected and the fault table is read. When this occurs, a description of the faults stored by the ECU are listed on the JDS screen and printed out on the JDS trace. An example is as follows:
The fault area is identified by finding the intersection of the bit column and fault table row marked with a 1. In the example above, a 1 at the intersection of bit column 0 and fault table row 6 indicates an "air pump" system electrical fault.



A cross reference guide of code information is on the following page:
After the fault table is printed, JDS determines if further testing is necessary. If JDS can determine the faulty component or circuit using only the serial communication link, a fault description will be given. If further testing is necessary, JDS will instruct the operator to do so.

When JDS asks the operator to test a faulty circuit, the following information applies:

^ The JDS screen will display "DO YOU WISH TO FIX THE FAULT AND CONTINUE TESTING".

^ "YES" should always be selected. If it is not, the fault table will be cleared when the test is exited.

^ After yes is selected, a fault description will be printed.

^ JDS will then clear the EMS fault table and test for permanent faults. Any permanent faults will re-appear after tbe ECU's memory has been cleared.

^ If an additional permanent fault exists, JDS will ask the operator to test the second fault, using the same procedure as above.


NOTE: If several faults were displayed on the JDS screen/trace in the beginning of the test and the faults are not detected by JDS after clearing the fault table, the conditions were intermittent or caused by the fault repaired previously.