Central Control Module (CCM)

Circuit Description

The Data Strobe Circuit provides the timing signal which causes the contents of the LCD's buffer to be displayed. This occurs after all 160 bits have been clocked into the LCD's buffer.

Upon power-up, the CCM pulls CKT 1368 low. It is then sent high after 80 milliseconds. After another 40 milliseconds, if it is still low, Code 36 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 an open, random characters will be displayed and the cluster display will be "frozen"; if there is a short to ground, the cluster display will flash random digits of the LCD.

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".