Chart B-5 and B-6 CRTC Problem

Chart B-5 & B-6 - CRTC Problem:

Wiring Diagram For Charts B-2, B-3, B-4, B-5 & B-6:

CHART B-5 - CRTC PROBLEM

Circuit Description:

Since all we can get on the CRT is a Radio Function page and we know the system is communicating as there is no "Electrical Problem" telltale and the speedometer is displaying zero, there must be a problem with the CRTC's ignition-on wake-up.


Test Description:

1. By grounding the circuit at the BCM we are doing what the BCM should be doing. If the CRT now works the BCM connector or BCM is fault.

2. If the CRT still does not work, grounding the circuit at the CRTC will check the integrity of CKT 738. If the CRT still does not work the CRTC connector or CRTC is faulty.


CHART B-6 - CRTC PROBLEM

Circuit Description:

Since the CRT screen is blank but the IPC speedometer displays zero we know the system is communicating but the CRT is unable to display even Radio functions which do not require the rest of the system.


Test Description:

1. Because we have already established that the BCM and IPC are communicating, if the "Electrical Problem" telltale is on it is due to loss of data to the CRTC. If "Electrical Problem" telltale is off the fault is within the CRT-CRTC. (See Chart C-1)

2. We know the problem is not a data line as this would not prevent radio functions, for the same reason it is also not the ignition-on (wake-up) circuit. It cannot be that the CRTC lost its grounds as in this case it would stop all communication and the IPC would show a blank speedometer. The only thing left is loss of CPS 12 volts. This must be an open circuit as a short would stop all 12 volts out of CPS and the "Service Engine Soon" light would not have worked.