DTC P1602 Lost Communications with Brake/Traction Control (EBTCM) System. Buick Regal (China) 2000

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2000 🢒 Regal (China) 🢒 Engine 🢒 Engine Controls - 2.5L (LB8) and 3.0L (L46) 🢒 DTC P1602 Lost Communications with Brake/Traction Control (EBTCM) System

Circuit Description

A class 2 serial data communications system is used on this vehicle to allow various modules to communicate and share information with each other. This allows vehicle wiring to be reduced and the transmission and reception of multiple signals over a single wire. The messages carried on a class 2 serial data streams are also prioritized. If two messages attempt to establish communications on the data line at the same time, the message with the higher priority will continue. The message with the lower priority message will wait. If a module cannot respond to the Powertrain Control Module (PCM), a DTC is stored.

Conditions for Running the DTC

•	The ignition is ON.

•	System voltage is more than 8.2 volts.

Conditions for Setting the DTC

The PCM is detecting a loss of serial data from the EBCM for more than 5 seconds.

Action Taken When the DTC Sets

•	The PCM will not illuminate the malfunction indicator lamp (MIL).

•	The PCM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC

•	A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

•	The DTC can be cleared by using the scan tool Clear Info function.

Diagnostic Aids

If no password is received a DTC P1610, P1626, and P1631 may be set.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation.

Any circuitry, that is suspected as causing an intermittent complaint, should be thoroughly inspected for the following items:

•	Backed out terminals or improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Poor terminal to wiring connections

•	Physical damage to the wiring harness

•

Corrosion

Step	Action	Values	Yes	No
1	Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Important: If a loss of data link communication (DLC) data has already been diagnosed using the DLC diagnosis table, clear this DTC and continue diagnosis with the Powertrain On Board Diagnostic (OBD) System Check . Attempt to select the ABS data with the scan tool. Can the ABS data be displayed?	--	Go to Step 3	Go to Step 4
3	Turn OFF the ignition switch. Disconnect the PCM and the EBCM/EBTCM. Inspect the serial data circuit for an open between the EBCM/EBTCM and the PCM. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found?	--	Go to Step 6	Go to Diagnostic Aids
4	Inspect the serial data circuit for a poor connection at the EBCM/EBTCM. If a problem is found, repair as necessary. Refer to Testing for Continuity , Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals and Connector Repairs in Wiring Systems. Was a problem found?	--	Go to Step 6	Go to Step 5
5	Inspect the serial data circuit for a poor connection at the PCM. If a problem is found, repair as necessary. Refer to Testing for Continuity , Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals and Connector Repairs in Wiring Systems. Was a problem found?	--	Go to Step 6	Go to Diagnostic System Check - ABS in Antilock Brake System
6	Review and record the scan tool Failure Records data. Clear the DTCs. Operate the vehicle within the Failure Records conditions. Using a scan tool, monitor Specific DTC info for DTC P1602. Does the scan tool indicate DTC P1602 failed?	--	Go to Step 2	System OK