DTC U1016 Loss of Communications with PCM. Buick Regal (China) (CNG) 1999

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1999 🢒 Regal (China) (CNG) 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC U1016 Loss of Communications with PCM

Circuit Description

Class 2 control modules receive a state of health message from the Powertrain Control Module (PCM) through the Class 2 serial data link.

Conditions for Setting the DTC

Class 2 control modules do not receive a state of health message from the PCM after receiving other messages from the PCM.

Action Taken When the DTC Sets

•	Class 2 control modules store DTC U1016 in memory.

•	The SERVICE VEHICLE SOON indicator lamp turns on.

Conditions for Clearing the DTC

•	DTC U1016 changes the status from current to history when class 2 control modules detect a state of health message from the PCM.

•	Using a scan tool.

Diagnostic Aids

•	The following conditions may cause an intermittent malfunction to occur:

•	An intermittent open, short to ground, or short to B+ in circuit 1049.

•	Poor connections at the PCM.

•	Control modules may store DTC U1016 if certain diagnostics are performed between the Powertrain Control Module (PCM) and the Data Link Connector (DLC).

•	DTC P1626 will set in the Powertrain Control Module (PCM) when the ignition switch is on with the Body Control Module (BCM) disconnected. When BCM diagnostics and repairs are completed, refer to OBD System Check in Engine Controls for additional information on PCM related DTCs.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This step checks for an open in the Splice Pack SP205.

This step checks for a short to ground in circuit 1049.

This step checks for a short to B+ in circuit 1049.

This step checks for an open in circuit 1049.

Step

Action

Value(s)

Yes

Turn the ignition switch off.
Disconnect the scan tool from the DLC.
Disconnect battery negative terminal.
Using a DMM, measure the resistance between the SP205 terminal A and each of the SP205 terminals B, E, G, L, and M; one terminal at a time.

Is the resistance measured within the specified range?

Less than 2ohms

Go to Step 2

Go to Step 6

Disconnect the Powertrain Control Module (PCM) connector C1.
Using a DMM, measure the resistance between the SP205 harness connector terminal B and ground.

Is the resistance measured same as the specified value?

∞

Go to Step 3

Go to Step 7

Reconnect the battery negative terminal.
Turn the ignition switch on.
Using a DMM, measure the voltage between the SP205 harness connector terminal B and ground.

Is the voltage measured within the specified range?

Less than 2V

Go to Step 4

Go to Step 8

Turn the ignition switch off.
Using a DMM, measure the resistance between the SP205 harness connector terminal B and the PCM harness connector C1 terminal 58.

Is the resistance measured within the specified range?

Less than 5ohms

Go to Step 5

Go to Step 9

Reconnect the PCM connector C1.
Turn the ignition switch on.
Using a scan tool, communicate with the PCM.

Does the scan tool communicate with PCM?

Go to Step 11

Go to Step 10

Replace the Splice Pack SP205.

Is the repair complete?

Go to Step 11

Repair short to ground in circuit 1049.

Is the repair complete?

Go to Step 11

Repair short to B+ in circuit 1049.

Is the repair complete?

Go to Step 11

Repair poor connection or open in circuit 1049.

Is the repair complete?

Go to Step 11

•	The integrity of the class 2 serial data link is OK. However, the Powertrain Control Module (PCM) is not communicating class 2 data due to a fault within the PCM.

•	Refer to A Powertrain On Board Diagnostic (OBD) System Check (VIN M) or A Powertrain On Board Diagnostic (OBD) System Check (VIN K, 1) for further diagnosis.

Is the action complete?

Go to Step 11

Turn the ignition switch off.
Reinstall connectors/components removed and verify repairs.

Is the action complete?

System OK