DTC P0608. Cadillac SLS 2008

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2008 🢒 SLS 🢒 Driver Information and Entertainment 🢒 Displays and Gages 🢒 DTC P0608

DTC P0608 LY7

Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC 0608: Vehicle Speed Output Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage
Vehicle Speed Signal Circuit	P0608	P0608¹	P0608
¹Speedometer and/or Odometer Inaccurate or Inoperative

The engine control module (ECM) creates the vehicle speed output signal by pulsing the circuit to ground. The ECM monitors the voltage on the vehicle speed output circuit in order to determine whether the voltage is out of the normal operating range. The instrument cluster receives the vehicle speed data from the ECM via the serial data circuit, and displays on the speedometer. Radio, rear parking assist module and inside rearview mirror (ISRVM) connectors receive the vehicle speed data through a separate vehicle speed signal circuit wire from the ECM. If the ECM determines that the voltage is out of the normal operating range, a DTC sets. Radio, rear parking assist module and inside rearview mirror (ISRVM) connectors determine the vehicle speed by using the vehicle speed signal of certain pulse speed from the ECM.

Conditions for Running the DTC

•	Engine speed is more than 80 RPM.

•	The ignition 1 voltage is between 10-18 volts.

•	The ECM has already commanded the vehicle speed output signal ON and OFF at least once during the ignition cycle.

•	The signal is present between 2.9-57.6 seconds.

•	DTC P0608 runs continuously once the above conditions are met.

Conditions for Setting the DTC

Data List matches the vehicle speed parameter

•	The ECM detects that the signal circuit is open, shorted to ground, or shorted to voltage.

•	The above condition must be present for a minimum of 4 seconds.

Action Taken When the DTC Sets

The ECM records the operating conditions at the time when the diagnostic test fails. The ECM displays this information in the Failure Records on the scan tool.

Conditions for Clearing the DTC

•	The DTC becomes history when the conditions for setting the DTC are no longer present.

•	The history DTC clears after 40 malfunction free warm-up cycles.

•	The ECM receives the clear code command from the scan tool.

Reference Information

Schematic Reference

•	Instrument Cluster Schematics

•	Radio/Navigation System Schematics

•	Inside Rearview Mirror Schematics

•	Engine Controls Schematics

Connector End View Reference

•	Component Connector End Views

•	Entertainment/Communication Connector End Views

•	Window Systems Connector End Views

•	Engine Control Module Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

•	Scan Tool Data List

•	Scan Tool Data Definitions

Circuit/System Verification

Install the scan tool, start the engine with the vehicle drive wheels raised and place the transmission in drive or first gear. Refer to Lifting and Jacking the Vehicle . Verify if the speedometer value in the ECM Engine displayed on the scan tool.

Circuit/System Test

Important: Raise the vehicle drive wheels and place the transmission in drive or first gear. Refer to Lifting and Jacking the Vehicle .

With the ignition OFF, disconnect the harness connector at the rear parking assist control module.
Start the engine with the vehicle drive wheels raised and place the transmission into drive or first gear. Verify if the speedometer value in the ECM Engine Data List matches the vehicle speed parameter displayed on the scan tool.

⇒	If the speedometer value matches the vehicle speed parameter displayed on the scan tool, test the vehicle speed signal circuit for a short to voltage, a short to ground or an open/high resistance. If the circuit tests normal, replace the rear parking sensor control module.

With the ignition OFF, disconnect the harness connector at the inside rearview mirror (ISRVM).
Start the engine with the vehicle drive wheels raised and place the transmission into drive or first gear. Verify if the speedometer value in the ECM Engine Data List matches the vehicle speed parameter displayed on the scan tool.

⇒	If the speedometer value matches the vehicle speed parameter displayed on the scan tool, test the vehicle speed signal circuit for a short to voltage, a short to ground or an open/high resistance. If the circuit tests normal, replace the inside rearview mirror (ISRVM).

With the ignition OFF, disconnect the harness connector at the ECM C1 or C2.
With the ignition ON, test for 9-11 volts between the vehicle speed signal circuit and ground.

⇒	If less than 9 volts, test the vehicle speed signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.

⇒	If greater than 11 volts, test the vehicle speed signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the radio.

If all circuits test normal, test or replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup and programming

DTC P0608 LH2