Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the DLC allows communication with the modules for diagnostic purposes.
The engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running.
The number(s) below refer to the step number(s) on the diagnostic table.
A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit.
The DTC U1300 and U1301 may be retrieved with a history status. These DTCs are not the cause of the present condition.
A State of Health DTC with a history status may be present along with a U1000 or a U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
The memory seat module (MSM), and the remote function actuator (RFA) are not monitored by other modules. When one of these modules is not communicating, diagnose the malfunction using the specified procedure.
Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
An open in the class 2 serial data circuit between the DLC and splice S203 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
If there are no current DTCs that begin with a U, the communication malfunction has been repaired.
The communication malfunction may have prevented diagnosis of the customer complaint.
Step | Action | Yes | No | ||||
---|---|---|---|---|---|---|---|
1 | Does the scan tool power up? | Go to Step 2 | |||||
2 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 3 | Go to Step 8 | ||||
3 |
Did you record any DTCs in the range of U1000 to U1305? | Go to Step 4 | Go to Step 7 | ||||
4 | Are the DTCs U1300, U1301 or U1305 retrieved from any module? | Go to Step 5 | Go to Step 6 | ||||
5 |
Important:: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems: Did you find and correct the condition? | Go to Step 54 | Go to Step 6 | ||||
6 | Are U1000 or U1255 the only DTCs displayed in the previously specified range? | Go to DTC U1000 and DTC U1255 Class 2 Communication Malfunction | |||||
7 | Diagnose the malfunction using the DTC U1XXX Loss of XXX Communications procedures for the module which is not communicating. Refer to DTC U1001-U1254 Loss of XXX Communications . Did you complete the action? | Go to Control Module References for the applicable Diagnostic System Check. | -- | ||||
8 |
Did you find and correct the condition? | Go to Control Module References for the applicable Diagnostic System Check. | Go to Step 9 | ||||
9 | Test the ground circuit at terminal 5 of the DLC for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Control Module References for the applicable Diagnostic System Check. | Go to Step 10 | ||||
10 | Test the class 2 serial data circuit for an open or short to ground or voltage between the DLC and splice S203. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Control Module References for the applicable Diagnostic System Check. | Go to Step 11 | ||||
11 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 12 | Go to Step 13 | ||||
12 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls. Did you complete the repair? | Go to Step 54 | -- | ||||
13 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 14 | Go to Step 16 | ||||
14 | Test the class 2 serial data circuit between the EBCM and the PCM for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 15 | ||||
15 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement in Antilock Brake System. Did you complete the repair? | Go to Step 54 | -- | ||||
16 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 17 | Go to Step 18 | ||||
17 | Replace the radio. Refer to Radio Replacement in Entertainment. Did you complete the repair? | Go to Step 54 | -- | ||||
18 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 19 | Go to Step 20 | ||||
19 | Replace the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console. Did you complete the repair? | Go to Step 54 | -- | ||||
20 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 21 | Go to Step 23 | ||||
21 | Test the class 2 serial data circuit between the instrument cluster and the CCP for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 22 | ||||
22 | Replace the CCP. Refer to Control Assembly Replacement in HVAC System--Automatic. Did you complete the repair? | Go to Step 54 | -- | ||||
23 | Is the vehicle equipped with A45? | Go to Step 24 | Go to Step 27 | ||||
24 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 25 | Go to Step 27 | ||||
25 | Test the class 2 serial data circuit between the MMM and the CCP for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 26 | ||||
26 | Replace the MMM. Refer to Memory Mirror Module Replacement in Doors. Did you complete the repair? | Go to Step 54 | -- | ||||
27 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 28 | Go to Step 30 | ||||
28 | Test the class 2 serial data circuit between the heater and A/C programmer (HCM) and the following component:
for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 29 | ||||
29 | Replace the heater and A/C programmer (HCM). Refer to Programmer Replacement in HVAC System--Automatic. Did you complete the repair? | Go to Step 54 | -- | ||||
30 | Is the vehicle equipped with a cellular telephone module? | Go to Step 31 | Go to Step 33 | ||||
31 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 32 | Go to Step 33 | ||||
32 | Replace the cellular telephone module. Refer to Radio Frequency Booster and Bracket Assembly Replacement in Cellular Communication. Did you complete the repair? | Go to Step 54 | -- | ||||
33 | Is the vehicle equipped with A45? | Go to Step 34 | Go to Step 37 | ||||
34 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 35 | Go to Step 37 | ||||
35 | Test the class 2 serial data circuit between the MSM and the radio for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 36 | ||||
36 | Replace the MSM. Refer to Memory Seat Control Module Replacement in Seats. Did you complete the repair? | Go to Step 54 | -- | ||||
37 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 38 | Go to Step 40 | ||||
38 | Test the class 2 serial data circuit between the SDM and the following component:
for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 39 | ||||
39 | Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement in SIR. Did you complete the repair? | Go to Step 54 | -- | ||||
40 | Is the vehicle equipped with F45? | Go to Step 41 | Go to Step 43 | ||||
41 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 42 | Go to Step 43 | ||||
42 | Replace the CVRSS module. Did you complete the repair? | Go to Step 54 | -- | ||||
43 | Is the vehicle equipped with UQ4? | Go to Step 44 | Go to Step 48 | ||||
44 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 45 | Go to Step 48 | ||||
45 | Is the vehicle equipped with F45? | Go to Step 46 | Go to Step 48 | ||||
46 | Test the class 2 serial data circuit between the CVRSS module and the RIM for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 47 | ||||
47 | Replace the RIM. Refer to Radio Speaker Amplifier Replacement in Entertainment. Did you complete the repair? | Go to Step 54 | -- | ||||
48 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 49 | Go to Step 52 | ||||
49 | Is the vehicle equipped with F45 or UQ4? | Go to Step 50 | Go to Step 51 | ||||
50 | Test the class 2 serial data circuit between the RFA module and the following component:
for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 51 | ||||
51 | Replace the RFA module. Refer to RFA Module Replacement in Keyless Entry. Did you complete the repair? | Go to Step 54 | -- | ||||
52 | Test the class 2 serial data circuit between the following:
for a short to ground or voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 54 | Go to Step 53 | ||||
53 | Replace the PZM. Refer to Body Control Module Replacement in Body Control System. Did you complete the repair? | Go to Step 54 | -- | ||||
54 |
Important: The scan tool may require a power up reset before communication will occur. Turn off or disconnect the scan tool before you display DTCs. Did you record any DTCs which begin with a U and with a current status? | Go to Step 56 | Go to Step 55 | ||||
55 | Did you record any DTCs which do not begin with a U? | Go to Step 56 | Go to Step 58 | ||||
56 | Diagnose the DTCs as directed by the diagnostic procedures for the particular module or malfunction. The PCM may have DTC(s) P1602 to P1615, or P1626 set. If only P1600 DTC(s) in the range specified along with history U1xxx DTC(s) are set and the vehicle will start and run, the action is complete. Did you complete the action? | Go to Step 57 | -- | ||||
57 | Did you diagnose all of the DTCs? | Go to Step 58 | Go to Step 56 | ||||
58 | Use the scan tool in order to clear the DTCs. Did you complete the action? | System OK | -- |