1992 Code 74
10-17-2017, 06:53 PM
#1
Melting Slicks
Thread Starter
1992 Code 74
1992 Code 74.....LED dimming output Circuit (Circuit open or shorted to ground)
Two things just happened simultaneously on my 92; once at idle, and once while driving:
• Lost all electrical power (including radio presets), and the engine died. Started up again immediately.
• Code 74 came up.
Once restarted, all functions and engine power were normal.
Page 8D-77 of the FSM outlines the troubleshooting process, the first of which is to confirm that the dimmer still works. It does. It's the next step that I want to avoid if I can.....'Remove the radio head', in order to put a test light between B+ and 7-way connector terminal 2. Is there an easier way to do this? Could this problem have been caused by something like a bad ground? (Battery terminals are clean and tight.)
Worst case repair solutions are to either replace the CCM or the radio control head. Any advice would be appreciated.
Two things just happened simultaneously on my 92; once at idle, and once while driving:
• Lost all electrical power (including radio presets), and the engine died. Started up again immediately.
• Code 74 came up.
Once restarted, all functions and engine power were normal.
Page 8D-77 of the FSM outlines the troubleshooting process, the first of which is to confirm that the dimmer still works. It does. It's the next step that I want to avoid if I can.....'Remove the radio head', in order to put a test light between B+ and 7-way connector terminal 2. Is there an easier way to do this? Could this problem have been caused by something like a bad ground? (Battery terminals are clean and tight.)
Worst case repair solutions are to either replace the CCM or the radio control head. Any advice would be appreciated.
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92ragtop (10-18-2017)
10-23-2017, 02:34 PM
#3
Melting Slicks
Thread Starter
TTT
OK, the connections at the power block by the battery are clean and tight. Anyone have other ideas about an easier way to diagnose a code 74 in a 1992?
OK, the connections at the power block by the battery are clean and tight. Anyone have other ideas about an easier way to diagnose a code 74 in a 1992?
10-23-2017, 02:42 PM
#4
Melting Slicks
Member Since: Jan 2014
Location: Downers Grove Illinois
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Do you have an H74 and/or C74? Do you have the C68 automatic climate control?
I saw the following that may apply to you:
CCM (Central Control Module) Codes 72 and 74 usually occur after the radio control head was replaced. The radio head LED and LCD open circuits are noticed by the CCM, setting the code. There is a simple fix while the radio head is being replaced. Resistors and one diode must be installed to alleviate the problem. A 1K 1/2 watt resistor is installed in the following manner: one side of the resistor must be powered by the radio head C2 connector in position 8 (pink wire). Connect one end of the resistor to this wire. This will send the correct voltage signal to the CCM once the other side of the resistor is connected. At radio head connector C1, locate the gray/black striped wire at position 3. Connect the other end of the resistor here. Be careful: the radio head has two gray/black striped wires in connector C1. The gray/black striped wire at position 4 is the incandescent lamp control. It will not set a code when left disconnected. To recap: the resistor will be installed at connector C2 position 8 on one end and connector C1 at position 3 for the other end.
I found it here under CCM Input and Output Testing section.
I saw the following that may apply to you:
CCM (Central Control Module) Codes 72 and 74 usually occur after the radio control head was replaced. The radio head LED and LCD open circuits are noticed by the CCM, setting the code. There is a simple fix while the radio head is being replaced. Resistors and one diode must be installed to alleviate the problem. A 1K 1/2 watt resistor is installed in the following manner: one side of the resistor must be powered by the radio head C2 connector in position 8 (pink wire). Connect one end of the resistor to this wire. This will send the correct voltage signal to the CCM once the other side of the resistor is connected. At radio head connector C1, locate the gray/black striped wire at position 3. Connect the other end of the resistor here. Be careful: the radio head has two gray/black striped wires in connector C1. The gray/black striped wire at position 4 is the incandescent lamp control. It will not set a code when left disconnected. To recap: the resistor will be installed at connector C2 position 8 on one end and connector C1 at position 3 for the other end.
I found it here under CCM Input and Output Testing section.
Last edited by JimLentz; 10-23-2017 at 02:43 PM.
The following users liked this post:
92ragtop (10-23-2017)
10-23-2017, 05:04 PM
#5
Melting Slicks
Thread Starter
Do you have an H74 and/or C74? Do you have the C68 automatic climate control?
I saw the following that may apply to you:
CCM (Central Control Module) Codes 72 and 74 usually occur after the radio control head was replaced. The radio head LED and LCD open circuits are noticed by the CCM, setting the code. There is a simple fix while the radio head is being replaced. Resistors and one diode must be installed to alleviate the problem. A 1K 1/2 watt resistor is installed in the following manner: one side of the resistor must be powered by the radio head C2 connector in position 8 (pink wire). Connect one end of the resistor to this wire. This will send the correct voltage signal to the CCM once the other side of the resistor is connected. At radio head connector C1, locate the gray/black striped wire at position 3. Connect the other end of the resistor here. Be careful: the radio head has two gray/black striped wires in connector C1. The gray/black striped wire at position 4 is the incandescent lamp control. It will not set a code when left disconnected. To recap: the resistor will be installed at connector C2 position 8 on one end and connector C1 at position 3 for the other end.
I found it here under CCM Input and Output Testing section.
I saw the following that may apply to you:
CCM (Central Control Module) Codes 72 and 74 usually occur after the radio control head was replaced. The radio head LED and LCD open circuits are noticed by the CCM, setting the code. There is a simple fix while the radio head is being replaced. Resistors and one diode must be installed to alleviate the problem. A 1K 1/2 watt resistor is installed in the following manner: one side of the resistor must be powered by the radio head C2 connector in position 8 (pink wire). Connect one end of the resistor to this wire. This will send the correct voltage signal to the CCM once the other side of the resistor is connected. At radio head connector C1, locate the gray/black striped wire at position 3. Connect the other end of the resistor here. Be careful: the radio head has two gray/black striped wires in connector C1. The gray/black striped wire at position 4 is the incandescent lamp control. It will not set a code when left disconnected. To recap: the resistor will be installed at connector C2 position 8 on one end and connector C1 at position 3 for the other end.
I found it here under CCM Input and Output Testing section.
It was H74, and yes I have the auto climate control.