MACK Vmac-III Schematic

SCHEMATICS AND DIAGRAMS

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SCHEMATICS AND DIAGRAMS

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SCHEMATICS AND DIAGRAMS

SYSTEM CONNECTORS

The V-MAC£ III system utilizes many different
connector styles and sizes. The Vehicle
Electronic Control Unit (VECU), Engine
Electronic Control Unit (EECU), and the Serial
Communications Port connectors are the largest
connectors in the system, and are where the
majority of the V-MAC£ III system testing is
performed. This section illustrates the VECU,
EECU, and Serial Communications Port
connectors and includes charts with connector
terminal identification and functions. The charts
should not be used as a replacement for the
detailed tests that appear in this manual. The
charts are intended as an identification reference
for use when repairing a connector or terminal.

6-Pin Serial Communication Port

The Serial Communications Port is a six (6) pin
connector used for system diagnostics and
reprogramming. It is located under the dashboard
to the left of the steering column. This port is used
for connecting a diagnostic computer to the
vehicle. See the illustration for the pin locations. A
listing of the signal on each pin follows the
illustration.

858

Figure 858 — 6-Pin Serial Communication Port

9-Pin Serial Communication Port

The Serial Communications Port is a nine (9) pin
connector used for system diagnostics and
reprogramming. It is located under the dashboard
to the left of the steering column. This port is
used for connecting a diagnostic computer to the
vehicle. See the illustration for the pin locations. A
listing of the signal on each pin follows the
illustration.

859

Figure 859 — 9-Pin Serial Communication Port

PIN Letter Designation

A Serial data link PLUS (+) line

B Serial data link MINUS (−) line

C PLUS (+) 12 volts

D Accessory relay

E Chassis ground

F Not used

PIN Letter Designation

A Chassis ground

B PLUS (+) 12 volts

C J1939 Serial data link PLUS (+) line

D J1939 Serial data link MINUS (−) line

E J1939 Serial data link shield line

F J1587 Serial data link PLUS (+) line

G J1587 Serial data link MINUS (−) line

H Not used

J Not used

SCHEMATICS AND DIAGRAMS

Page 719

Vehicle Electronic Control Unit
(VECU) Connectors

The Vehicle Electronic Control Unit (VECU) has
three 18 pin connectors. Each pin is marked on
the inside of the connector. To disconnect a
connector from the VECU, press down on the
tang of the harness connector and gently pull the
connector from the VECU. Be sure that the
connector is aligned as shown below to avoid
confusion when checking pin numbers. The
connector number and color are shown as a
reference for reconnecting the VECU to the cab
harness.

860

Figure 860 — VECU Connectors

VEHICLE ELECTRONIC CONTROL UNIT
(VECU) CONNECTOR PIN DESIGNATIONS

VECU Connector J1

PIN

Number Description

1 Ignition key switch

2 Starter signal

3 Buffered vehicle speed output

(Speedometer Signal)

4 Buffered RPM output (Tachometer Signal)

5 Shutdown override signal

6 Speed control ON/OFF switch signal

7 Speed control SET/DECEL signal

8 Speed control RESUME/ACCEL signal

9 Clutch engaged signal

10 Parking brake signal (#1)

11 Service brake signal

12 Engine brake switch — low

13 Engine brake switch — high

14 Not used

15 Fan clutch override

16 Not used

17 Not used

18 Fuel level sensor signal