Pinpoint Tests AC: Incorrect Speedometer Indication
Instrumentation, Message Center and Warning Chimes
Pinpoint Test AC: Incorrect Speedometer Indication
Normal Operation
The PCM receives the vehicle speed data from the Output Shaft Speed (OSS). The PCM provides the Instrument Cluster (IC) with the Vehicle Speed Sensor (VSS) signal over the High Speed Controller Area Network (HS-CAN) communication bus. The IC monitors the VSS input from the PCM and commands the speedometer with a corresponding movement of the pointer. Factors that could potentially affect the accuracy of the speedometer are configurable items such as tire size.
This pinpoint test is intended to diagnose the following:
- Axle ratio
- Tire size
- PCM
- IC
PINPOINT TEST AC: INCORRECT SPEEDOMETER INDICATION
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AC1 CHECK FOR CORRECT AXLE RATIO AND TIRE SIZE CONFIGURATION
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Module Programming.
- Select programmable parameters and confirm that the axle ratio and the tire size are correctly configured.
- Are the axle ratio and tire size correctly configured?
Yes
GO to AC2.
No
CONFIGURE the axle ratio or tire size as required. TEST the system for normal operation.
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AC2 RETRIEVE THE RECORDED DTCs FROM THE PCM KOEO SELF-TEST
- Check the recorded PCM DTCs from the Key ON Engine OFF (KOEO) self-test.
- Are any DTCs recorded?
Yes
REFER to Computers and Control Systems Information.
No
GO to AC3.
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AC3 CARRY OUT THE SPEEDOMETER ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IC DataLogger.
- Select the IC speedometer (SPDOMETER) active command and command the speedometer 0, 193 km/h (120 mph), and back to 0.
- Does the speedometer reading start at 0 and move to 193 km/h (120 mph), and return to 0?
Yes
GO to AC4.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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AC4 CHECK THE IC VSS INPUT
- Ignition ON.
- Enter the Instrument Cluster (IC) Dealer Test Mode.
- NOTE: The display below uses xxx's to represent a numeric or alpha-numeric value. The value may display the same amount of characters represented by the xxx's or there may be more/less depending on the type of display. For example: E xxx.x (base cluster) or xxx.x MPH (message center cluster) may display E 25 (base cluster) or 25 MPH (message center cluster). Note that there were 3 x's in the display description but only 2 digits in the actual display.
- Scroll through the displays to E xxx.x (base cluster) or xxx.x MPH (message center cluster).
- Monitor the speedometer and the vehicle speed input at various vehicle speeds.
- Does the speedometer approximately match the vehicle speed input?
Yes
INSTALL a new PCM. TEST the system for normal operation.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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