My 2003 Cadillac CTS wont come out of park and the traction control light and the ABS light are on

SOGMCGG1

MEMBER
2003 CADILLAC CTS
40,000 MILES

My 2003 Cadillac cts wont come out of park and the traction control light and the abs light are on, sometimes the lights will go out and the the car shifts out of park fine. This all started when I had a blow out on my front drivers side tire after changing the tire the car would not shift out of park, after one or two times restarting the car the lights went out and it started. Now it's getting worse and today I was stuck for 2 hours and cant place my finger on what it could be? Thanks Charlie

codes p0856, p0318, u1040.

1 Reply

RIVERMIKERAT

MECHANIC
6,110 POSTS

P0318-Loss of Communication-Rough road data
P0856-No listing.
U1040-Brake system module communication error.
ENGINE CONTROLS - SELF-DIAGNOSTICS -2003 Cadillac CTS
Page 1 of 2
DTC P0318: LOSS OF COMMUNICATION - ROUGH ROAD DATA

NOTE:
To locate components, see COMPONENT LOCATIONS. For circuit
reference, see WIRING DIAGRAMS. For connector terminal identification,
see CONNECTOR IDENTIFICATION. If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If
testing requires component removal or replacement, see appropriate
REMOVAL & INSTALLATION article.
Description

Rough roads cause torque on the tires that is transmitted to the powertrain. This slows down the crankshaft giving the appearance of a misfire. The Electronic Brake Control Module (EBCM)
determines rough road surfaces using input from the wheel speed sensors. The EBCM then sends the rough road data to the Engine Control Module (ECM) via class 2 serial data. The data allows the ECM
to distinguish the crankshaft speed variations caused by rough road surfaces from those caused by true misfires. If a loss of communication occurs that causes the ECM not to receive rough road information
while a misfire condition is requesting the Malfunction Indicator Lamp (MIL), DTC P0318 will set.
Conditions For Running DTC

DTC P0300 is occurring and requesting the MIL to be illuminated.
Conditions For Setting DTC

The ECM is detecting a loss of communication with the EBCM for approximately 12 seconds or more.
Action Taken When DTC Sets

? The control module stores the DTC information into memory when the diagnostic runs and fails. ? The Malfunction Indicator Lamp (MIL) will not illuminate.
? The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
? The driver information center, if equipped, may display a message.
Conditions For Clearing DTC

? The ECM turns OFF the MIL after 3 consecutive drive trips that the diagnostic runs and does not fail within the same conditions that the DTC last failed.
? A History DTC clears after 40 consecutive warm-up cycles if no failures report by this diagnostic or any other emission related diagnostic.
? The DTC can be cleared with a scan tool.
Test Description

12/30/2011
ENGINE CONTROLS - SELF-DIAGNOSTICS -2003 Cadillac CTS
Page 2 of 2
The number below refers to the step in the diagnostic procedure.
2

This step ensures that the EBCM is capable of transmitting serial data on the class 2 serial data circuit.
Diagnostic Procedure

Fig. 127: DTC P0318: Loss Of Communication - Rough Road Data Courtesy of GENERAL MOTORS CORP.