Pinpoint Test F: Incorrect Speedometer Indication
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test F: Incorrect Speedometer Indication
Normal Operation
The PCM calculates vehicle speed from the transmission Output Shaft Speed (OSS) sensor input and from the tire size and axle ratio configuration in the Vehicle Identification (VID) block of the PCM. 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 and axle ratio.
The IC provides a tolerance which biases the speed indication and allows the gauge to display between 3% lower and 7% higher than the actual vehicle speed. This means that with an actual vehicle speed of 96.6 km/h (60 mph), the speedometer may indicate between 93.7-103.3 km/h (58.2-64.2 mph). Other factors that could potentially affect the speedometer accuracy are incorrect tire size, tire size configuration and axle ratio configuration.
This pinpoint test is intended to diagnose the following:
- Tire size configuration
- Axle ratio configuration
- PCM concern
- IC
PINPOINT TEST F: INCORRECT SPEEDOMETER INDICATION
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F1 OBSERVE THE SPEEDOMETER OPERATION
- Observe the speedometer while driving the vehicle at various speeds and stopping frequently.
- Does the speedometer begin at 0 km/h (0 mph), indicate the different vehicle speeds and fully return to the 0 km/h (0 mph) position when the vehicle is stopped?
Yes
GO to F2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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F2 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 F3.
No
CONFIGURE the axle ratio or tire size as required. TEST the system for normal operation.
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F3 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 F4.
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F4 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. Command the speedometer in 10% increments while monitoring the speedometer. The speed indicated should increase in increments of approximately 19.2 km/h (12 mph) for each 10% change.
- Does the speed indicated increase within specifications?
Yes
GO to F5.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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F5 MONITOR THE VSS PID
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- Select the PCM PID (VSS). Monitor the vehicle speed PID while driving the vehicle.
- Does the vehicle speed PID match the speedometer reading on the IC?
Yes
The speedometer is operating correctly at this time.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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