CCM (central control module)
Burning Brakes
Joined: Jul 2002
Posts: 1,050
Likes: 59
From: McLean Va
Originally Posted by Hooked on Vettes
H31 is a problem in the LCD Data Circuit.
H means it's a History code and not current.
Some codes always set as a history code but the manual doesn't say if 31 is always a history code.
Code 31 will set if Circuit 1932 (Gray wire) is not in a low state 80 milliseconds after the CCM powers up.
The LCD Data circuit is a signal line from the CCM to the instrument cluster.
If the circuit is shorted to B+ (12 volt power source)
or the CCM driver is open, all segments of the LCD digits will be OFF.
Is there anything wrong with the LCD display?
If not, the problem is intermittant. Clear the code and see if it comes back.
If the problem is a hard failure, the manual says to
1) Turn the ignition on and measure Pin A12 at the cluster plug.
If you measure 12 volts, repair short to B+
If you measure 2 to 5 volts turn the ignition off
and disconnect pin A12 at the instrument cluster.
Place a 1200 ohm resistor to ground. Turn the ignition on. If error code 31 comes back, the CCM is at fault. Otherwise the problem is the Dash cluster.
H means it's a History code and not current.
Some codes always set as a history code but the manual doesn't say if 31 is always a history code.
Code 31 will set if Circuit 1932 (Gray wire) is not in a low state 80 milliseconds after the CCM powers up.
The LCD Data circuit is a signal line from the CCM to the instrument cluster.
If the circuit is shorted to B+ (12 volt power source)
or the CCM driver is open, all segments of the LCD digits will be OFF.
Is there anything wrong with the LCD display?
If not, the problem is intermittant. Clear the code and see if it comes back.
If the problem is a hard failure, the manual says to
1) Turn the ignition on and measure Pin A12 at the cluster plug.
If you measure 12 volts, repair short to B+
If you measure 2 to 5 volts turn the ignition off
and disconnect pin A12 at the instrument cluster.
Place a 1200 ohm resistor to ground. Turn the ignition on. If error code 31 comes back, the CCM is at fault. Otherwise the problem is the Dash cluster.
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,060
Likes: 0
From: Dixon Ca
Originally Posted by Hooked on Vettes
Well it sounds like you did clear the codes.
Module 1 is the CCM and if all you see is C12, that indicates you're in the CCM Diagnostic mode and there are no error codes stored.
Module 4 is the ECM and ---- indicates no codes.
Module 9 is the EBCM Electronic Brake Control Module
(Anti Lock brake) and ---- indicates no codes.
Module 1 is the CCM and if all you see is C12, that indicates you're in the CCM Diagnostic mode and there are no error codes stored.
Module 4 is the ECM and ---- indicates no codes.
Module 9 is the EBCM Electronic Brake Control Module
(Anti Lock brake) and ---- indicates no codes.
