MBE 900 4000 Troubleshooting – Section 5.2 Troubleshooting PID 84

Section 5.2
Troubleshooting PID 84

The following procedure will troubleshoot PID 84.‪

Section 5.2.1
084 03 – Open Circuit

Perform the following steps to troubleshoot an open circuit.‪

1. Measure the voltage between wires 439S- and 439S+. See Figure "Vehicle Speed Sensor Wiring" .
   

   Figure 1. Vehicle Speed Sensor Wiring

   1. If battery voltage was not recorded, refer to "5.2.4 084 04 – Faulty Vehicle Speed Sensor" .
   2. If battery voltage was recorded, go to step 2 .
2. What fault code was active when bridging the disconnected VSS wires? Go to step 3 .
3. What fault is active when bridging wire 439S+ (at the VSS) to ground?
   1. If fault code 084 03 was recorded, refer to "5.2.2 084 03 – Faulty Vehicle Speed Sensor" for required steps.
   2. If no fault codes were recorded, refer to "5.2.4 084 04 – Faulty Vehicle Speed Sensor" for required steps.

Section 5.2.1.1
Required Action

Perform the following steps to resolve PID 84 fault code — 439S+ Open Circuit.‪

1. Repair and replace open circuit in VSS wire 439S+.
2. Erase the fault code memory.

Section 5.2.2
084 03 – Faulty Vehicle Speed Sensor

Perform the following steps to troubleshoot a faulty VSS.‪

1. Measure the battery voltage between wires 439S- and 439S+ at the VSS.
   1. If battery voltage was not recorded, refer to "5.2.4 084 04 – Faulty Vehicle Speed Sensor" .
   2. If battery voltage was recorded, go to step 2 .
2. What fault code is active when bridging the disconnected VSS wires?
   1. If fault 084 04 was recorded, refer to "5.2.4 084 04 – Faulty Vehicle Speed Sensor" .
   2. If no fault code was recorded, refer to "5.2.2.1 Required Actions" for required steps.

Section 5.2.2.1
Required Actions

Perform the following steps to resolve 084 03 Wire 439S- Open Circuit.‪

1. Replace the VSS.
2. Erase the fault code memory.

Section 5.2.3
084 03 – Short to Power

Perform the following steps to troubleshoot a short to power.‪

1. Measure for battery voltage between wires 439S- and 439S+ at the VSS.
   1. If battery voltage was not recorded, refer to "5.2.4 084 04 – Faulty Vehicle Speed Sensor" .
   2. If battery voltage was recorded, refer to "5.2.3.1 Required Actions" .

Section 5.2.3.1
Required Actions

Perform the following steps to resolve 084 03 — Wire 439S+ Short to Power.‪

1. Repair the short to power in VSS wire 439S+.
2. Erase the fault code memory.

Section 5.2.4
084 04 – Faulty Vehicle Speed Sensor

Perform the following step to troubleshoot a faulty VSS.‪

1. Check for active codes.
   1. If fault 084 04 was recorded after disconnecting the VSS and waiting more than 10 seconds, refer to "5.2.4.1 Required Actions" .
   2. If fault code 084 04 was not recorded after disconnecting the VSS and waiting more than 10 seconds, refer to "5.2.5 084 04 – Faulty DDEC-VCU" .

Section 5.2.4.1
Required Actions

Perform the following steps to resolve the 084 04 — Faulty VSS.‪

1. Replace the VSS.
2. Erase the fault code memory.

Section 5.2.5
084 04 – Faulty DDEC-VCU

Perform the following steps to troubleshoot a faulty DDEC-VCU. See Figure "Location of DDEC-VCU and Wiring Harness Connectors" .‪

1. Passenger-Side Dash‪	4. 18-Pin Connector‪
2. DDEC-VCU‪	5. 21-Pin Connector‪
3. 15-Pin Connector‪	‪

Figure 2. Location of DDEC-VCU and Wiring Harness Connectors

1. Disconnect the VSS.
2. Check for active codes.
   1. If fault code 084 04 was not recorded after disconnecting the VSS and waiting more than ten seconds, refer to "5.2.6 084 04 – Short to Ground" .
   2. If fault code 084 04 was recorded after disconnecting the VSS and waiting more than 10 seconds, refer to "5.2.5.1 Required Actions" .
3. Check for active codes.
   1. If fault code 084 04 was not recorded after disconnecting the 15-Pin connector, refer to "5.2.6 084 04 – Short to Ground" .
   2. If fault code 084 04 was recorded after disconnecting the 15-Pin connector, refer to "5.2.5.1 Required Actions" .

Section 5.2.5.1
Required Actions

Perform the following steps to resolve the 084 04 — Faulty DDEC-VCU.‪

1. Replace the DDEC-VCU.
2. Erase the fault code memory.

Section 5.2.6
084 04 – Short to Ground

Perform the following steps to troubleshoot the 084 04 Wire 439S+ short to ground.‪

1. Disconnect the VSS and wait ten seconds.
2. Check for active codes.
   1. If fault code 084 04 was not active after disconnecting the VSS and waiting ten seconds, refer to "5.2.7 084 04 – Short Between Wires 439S+ and 439S-" .
   2. If fault code 084 04 was active after disconnecting the VSS and waiting ten seconds, go to step 4 .
3. Disconnect the 15-Pin connector.
4. Check for active codes.
   1. If fault code 084 04 was not active after disconnecting the 15-Pin connector, refer to "5.2.7 084 04 – Short Between Wires 439S+ and 439S-" .
   2. If fault code 084 04 was active after disconnecting the 15-Pin connector, go to step 5 .
5. Measure for continuity between the VSS wires 439S+ and 439S-.
   1. If continuity was recorded between wires 439S+ and 439S-, refer to "5.2.7 084 04 – Short Between Wires 439S+ and 439S-" .
   2. If continuity was not recorded between wires 439S+ and 439S-, refer to "5.2.6.1 Required Actions" .

Section 5.2.6.1
Required Actions

Perform the following steps to resolve 084 04 Wire 439S+ Short to Ground.‪

1. Repair the short to ground in the VSS wire 439S+.
2. Erase the fault code memory.

Section 5.2.7
084 04 – Short Between Wires 439S+ and 439S-

Perform the following steps to troubleshoot 084 04 short between wires 439S+ and 439S-.‪

Note: The short could be between the DDEC-VCU and the Bulkhead connector or between the Bulkhead connector and the VSS.

1. Disconnect the VSS and wait ten seconds.
2. Check for active codes.
   1. If fault code 084 04 was not active, contact the Detroit Diesel Technical Support Group.
   2. If fault code 084 04 was active, go to step 4 .
3. Disconnect the 15-Pin connector.
4. Check for active codes.
   1. If fault code 084 04 was active, contact the Detroit Diesel Technical Support Group.
   2. If fault code 084 04 was not active, go to step 5 .
5. Measure for continuity between the VSS wires 439S+ and 439S-.
   1. If no continuity was measured, contact the Detroit Diesel Technical Support Group.
   2. If continuity was measured, refer to "5.2.7.1 Required Actions" .

Section 5.2.7.1
Required Actions

Perform the following steps to resolve 084 04 Short Between Wires 439S+ and 439S-.‪

1. Repair the short circuit in the VSS wires 439S+ and 439S-.
2. Erase the fault code memory.