Central Control Module (CCM)

Circuit Description

The Data Clock Circuit provides the timing signal which causes each of the 160 bits of the LCD data signal to be clocked into the buffer of the LCD display.

Upon power-up, the CCM pulls CKT 1367 low. After 80 milliseconds, it is sent high. If it is still low after the next 80 milliseconds, Code 34 will set.

Test Description

Number(s) below refer to circled number(s) on the diagnostic chart.

1. This test checks for a short to ground in the circuit.
2. This test checks for an open in the circuit.
3. This test replaces the cluster with a 1200 ohm resistance, very similar to the resistance of the cluster If the code comes back, the CCM must be at fault. If the code does not come back, the cluster must be the source of the problem.

Diagnostic Aids

If there is a short to ground, random segments of the LCD digits will be "ON," and the display will not update. If there is an open, all segments will be "ON" and the cluster display will be "frozen," or the LCD will be blank.

If the code is a history code, the problem may be intermittent. Try performing the tests shown while "wiggling" wiring and connectors; this can often cause the fault to appear. Refer to "Intermittents/Poor Connections".