Pinpoint Test AC: The Customer Access Speed Signal Input Is Inoperative

Commercial Service Equipment

Pinpoint Test AC: The Customer Access Speed Signal Input Is Inoperative

Refer to Wiring Diagrams Set 140, Customer Access for schematic and connector information. Electrical Diagrams

Normal Operation

The Instrument Cluster (IC) sends a signal to the customer access block connector for vehicle speed/distance information.

Similar to a typical wheel speed signal, when the vehicle is stopped, there is no signal (no voltage pulses). When the vehicle is moving, the faster the vehicle speed, the higher the voltage pulses are sent to the customer access block connector.

This pinpoint test is intended to diagnose the following:

- Customer-installed components or circuitry

- Wiring, terminals or connectors

- IC (Instrument Cluster)

PINPOINT TEST AC : THE CUSTOMER ACCESS SPEED SIGNAL INPUT IS INOPERATIVE

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

AC1 CHECK THE SPEEDOMETER OPERATION

- Check the operation of the speedometer.

Does the speedometer operate?

Yes
GO to AC2.

No
REFER to Instrument Panel, Gauges and Warning Indicators.

AC2 CHECK FOR A VOLTAGE SIGNAL TO THE CUSTOMER ACCESS BLOCK CONNECTOR

- Ignition OFF.

- Disconnect: Customer Access Block Connector C3509.

- Ignition ON.

- Measure the voltage between the customer access block connector C3509-2, circuit 8-NC8 (WH/BU), harness side and the customer access block connector C3509-10, circuit 31-LG12 (BK), harness side.





- Monitor the voltage while increasing the vehicle wheel speed.

Does the voltage increase with the vehicle wheel speed?

Yes
The vehicle is operating correctly. The concern is with the customer-installed components or circuitry.

No
GO to AC3.

AC3 CHECK THE VEHICLE SPEED SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE

- Ignition OFF.

- Disconnect: IC (Instrument Cluster) C220B.

- Ignition ON.

- Measure the voltage between the customer access block connector C3509-2, circuit 8-NC8 (WH/BU), harness side and ground.





Is any voltage present?

Yes
REPAIR the circuit. TEST the system for normal operation.

No
GO to AC4.

AC4 CHECK THE VEHICLE SPEED SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND

- Ignition OFF.

- Measure the resistance between the customer access block connector C3509-2, circuit 8-NC8 (WH/BU), harness side and ground.





Is the resistance greater than 10,000 ohms?

Yes
GO to AC5.

No
REPAIR the circuit. TEST the system for normal operation.

AC5 CHECK THE VEHICLE SPEED SENSOR SIGNAL CIRCUIT FOR A OPEN

- Measure the resistance between the customer access block connector C3509-2, circuit 8-NC8 (WH/BU), harness side and the IC (Instrument Cluster) C220B-3, circuit 8-NC8 (WH/BU), harness side.





Is the resistance less than 5 ohms?

Yes
GO to AC6.

No
REPAIR the circuit. TEST the system for normal operation.

AC6 CHECK FOR CORRECT IC (Instrument Cluster) OPERATION

- Disconnect all the IC (Instrument Cluster) connectors.

- Check for:
- corrosion

- damaged pins

- pushed-out pins


- Connect all the IC (Instrument Cluster) connectors and make sure they seat correctly.

- Operate the system and verify the concern is still present.

Is the concern still present?

Yes
INSTALL a new IC (Instrument Cluster). TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.