Circuit Description
When investigating any complaint of an instrument cluster problem or malfunction, always begin diagnosis with the diagnostic circuit check. This check is a preliminary procedure that checks that the instrument cluster is powered up, communicating on the serial data line, helping to identify a problem or malfunction and directing the reader to the appropriate diagnostic chart in this section. With the Tech 2 connected to the data link connector (DLC) and ignition switched on, the Tech 2 should display serial data communication. If the Tech 2 does not display serial data, the serial data circuit maybe open or shorted. There are several other control modules that are connected to the serial data line powertrain control module (PCM), powertrain interface module (PIM), body control module (BCM), antilock braking system (ABS)/traction control system (TCS), instrument cluster, radio and sensing and diagnostic module (SDM). Any of these control modules could cause a fault on the serial data line. This fault could result in the Tech 2 not being able to display serial data. DTC 14 will set if there is no serial data message on the serial data bus for more than 10 seconds. In practice, the trouble code is set somewhere between 10 and 20 seconds after the last serial data message is received by the instrument cluster. The trouble code is reset within 10 seconds of the arrival of an instrument cluster poll from the BCM. The DTC is logged as a History DTC.
Diagnostic Aids
A fault with the serial data circuit could be caused by one or more of the several control modules connected to this serial data circuit. Isolate the fault by disconnecting each control module, one at a time, until serial data communication is restored.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Instrument Cluster Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the Tech 2 display BCM information? | -- | Go to Step 3 | Go to Scan Tool Does Not Communicate with UART Data Line in Data Link Communications |
3 | Attempt to communicate with the body control module (BCM), powertrain control module (PCM), powertrain interface module (PIM) and instrument panel (I/P). Were you able to make contact with the specified modules? | -- | Go to Step 6 | Go to Step 4 |
4 | Using an ohmeter, back probe the BCM connector 2 Primary universal asynchronous receiver transmitter (UART) Serial Data circuit and the Secondary UART Serial Data circuits. Is the value as specified? | Less than 10 ohms | Go to Step 5 | Go to Step 8 |
5 | Inspect the Secondary UART Serial Data circuit for an open, short to ground or short to voltage between the BCM and individual control modules. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and complete the repair? | -- | Go to Step 9 | Go to Step 8 |
6 | Inspect the Secondary UART Serial Data circuit between the BCM and the I/P for continuity. Is continuity present? | -- | Go to Step 9 | Go to Step 8 |
7 | Inspect instrument cluster ground circuit for continuity to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 10 | -- |
8 | Repair the open or high resistance in the Secondary UART Serial Data circuit between the PCM and the PIM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 10 | -- |
9 | Replace the BCM. Refer to Body Control Module Replacement in Body Control Systems. Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
