DTC 38

Circuit Description

The M Clock Circuit carries a square wave signal which provides alternating voltage to the LCD's backplane; this is required for proper operation of the LCD.

Upon power-up, the CCM pulls CKT 1366 low. After 80 milliseconds, it is then sent to a high state. If it is low during the next 40 milliseconds, Code 38 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 or short to ground, some segments of the digits in the display will be "ON" and some will be "OFF"; some segments of the digits will be dim, and others will be full-brightness.

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".