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--- techtalk:evo:elec04 [2018/05/14 00:30]
ixl2relax [CANbus - Controller Area Network Bus]
+++ techtalk:evo:elec04 [2021/08/18 20:05] (current)
ixl2relax [SDB - Serial Data Bus]
@@ Line 11: / Line 11: @@
 In 2004, HD implemented the serial data bus (SDB) on all Sportster models. This single wire, digital communications link, provides a means for the Ignition Control Module (ICM), the Turn Signal Module (TSM/TSSM) and Speedometer/Tachometer to intelligently communicate with one another. There is a 4-pin 'port' connector (called a serial data link) to allow external computer connection to the SDB. It is located near the MaxiFuse.
-The SDB link allowed the ICM to be reprogrammable because it allowed the factory and the dealer the ability to use one ICM and program it for either 883 engines or 1200 engines. There are updates that can be dealer 'flashed' into the ICM when new parameters will resolve known problems.
+The SDB link allows the ICM to be reprogrammable - That allows the factory and dealer to use one stock-version ICM module and program it for use on either the 883 engines or 1200 engines. There are updates that can be dealer 'flashed' into the ICM when new parameters will resolve known problems.
 The ICM, TSM & Speedo/Tach regularly communicate their current status to one another. When all operating parameters on the serial data line are within specifications, a state of health message is sent between the components.
+A DTC of U1016 (Diagnostic Code) is set when the ICM can't send that 'state of health message'.\\
+--- That code is also set if there was communications, but it stopped at some point.\\
+A DTC of U1097 is set by the Speedo if it can't send the 'state of health message'.
+--- That code is also set if there was communications, but it stopped at some point.\\
+A DTC of U1255 is set when no messages are communicated at power up.\\
 The SDB is designed upon a standard SAE serial communication protocol callded "J1850". The digital data is transmitted and received on a single wire at around 10.4 Kbps. This protocol was used thru the 2013 model year.
@@ Line 22: / Line 29: @@
 **Checking SDB Link:**\\
-With ignition key switch turned ON, engine not running, transmit data should typically create a voltage on the SDB line (LtGreen/Violet Wire) of 0.6-0.8 volts. The range of voltages that might be seen as acceptable during operation is 0v - 7.0 volts.
+With ignition key switch turned ON, engine not running, transmit data should typically create a voltage on the SDB line (LtGreen/Violet Wire) of 0.6-0.8 volts. The range of voltages that might be seen as acceptable during operation is 0v - 7.0 volts, but you won't see that with a multimeter - you may need an O-scope to see those changes.
 \\
@@ Line 50: / Line 57: @@
 **Test - CANbus normal voltage:**\\
-With the keyswitch on, you can connect a meter (set for 20v readings) between Pin#1 (White/Red), or Pin#3 (White/Black), and ground to test for the 2.5v, which would be a normal reading on these lines.
+With the keyswitch on, you can connect a meter (set for 20v readings) between Pin#1 (White/Red), or Pin#3 (White/Black), and ground to test for the 2.5v, which would be a normal reading on these lines. If either line reads lower than 1.25v or higher than 3.75v, you may have a malfunctioning device or a short somewhere.
 **Test - CANbus shorted together:**\\
@@ Line 62: / Line 69: @@
 **Test - CANbus High shorted to power:**\\
-With the keyswitch on, you can connect a meter (set for 20v readings) between Pin#1 (White/Red) and ground. If the voltage is higher than 4v on CANbus High, you may have a short to voltage somewhere. By turning the keyswitch off, then removing one component from the CANbus, then turning the keyswitch back on, you can test to see if the voltage on DLC Pin#1 has normalized because you removed a malfunctioning CANbus component. Devices should be removed in the following order: Speedometer, ECM, LftHandControl, RtHandControl, Tach - If DLC Pin#1 has not normalized, then, with the keyswitch off, reconnect the ECM & disconnect power to the BCM, then disconnect the main connector from the BCM, then turn the keyswitch on and test the DLC pin again - If now normalized, the BCM is suspect.
+With the keyswitch on, you can connect a meter (set for 20v readings) between Pin#1 (White/Red) and ground. If the voltage is higher than 4v on CANbus High, you may have a short to voltage somewhere. By turning the keyswitch off, then removing one component from the CANbus, then turning the keyswitch back on, you can test to see if the voltage on DLC Pin#1 has normalized because you removed a malfunctioning CANbus component.
+Be sure to turn the keyswitch off when connecting or disconnecting devices. Devices should be removed in the following order: Speedometer, ECM, LftHandControl, RtHandControl, Tach - If DLC Pin#1 has not normalized, then, with the keyswitch off, reconnect the ECM & disconnect power to the BCM, then disconnect the main connector from the BCM, then turn the keyswitch on and test the DLC pin again - If now normalized, the BCM is suspect.

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