Riviera V6-231 3.8L VIN C SFI (1989)
No Picture Circuit
CIRCUIT DESCRIPTION:
Since the problem has been narrowed down to the CRT screen not being able to light, when using tester J34914 it is not necessary to go through the
whole test sequence, only see if the tester can illuminate the screen.
TEST DESCRIPTION: Numbers below refer to circled numbers on diagnostic chart.
1.
First noting if any of the border LEDs work will verify the integrity of the 12.0 volts from the CPS, as this circuit is used to operate the CRT and
feed the LEDs.
2.
Disconnecting the CRT from the vehicle and connecting the tester to the CRT will verify the integrity of the CRT. The only thing to look for here
is the ability of the CRT to light up. If it cannot light up with the tester connected, the CRT connector or CRT is at fault. Make sure the CRT
tester's fuse is not blown and the tester is working correctly.
3.
If no LED light, and the CRT did light with the tester, verify the integrity of he 12.0 volt circuit from the CPS to the CRT using the CRT's ground.
The problem must be power, ground or wake-up (turn "ON").
4.
If test light does not light, use a known good ground to determine if the problem is the 12.0 volt circuit or the CRT has lost its grounds.
5.
If the test light lights, when checking CRT 12.0 volt to CRT's ground, connecting the tester at the harness end at the CRTC will determine if the
wake-up (turn "ON") circuit from the CRTC to the CRT (including CRT terminal contact) is at fault or if the CRTC connector or CRT is at fault.
6.
We know power ground and wake-up signals are present as at least one LED lights, and the CRT is OK as the tester was able to light the screen.
Connecting the tester to the harness at the CRTC will determine if the CRTC COAX connector or CRT is at fault or if the video circuit is open or
short, or the dimming CKT is shorted to ground, or poor terminal contact at the CRT. Because the tester provides the dimming signal to the CRT
but returns control of the dimming signal to the BCM when tester is connected to harness at CRTC, a shorted to ground dimming CKT will cause a
blank CRT.
