Solution K75115306
Friday, January 4, 2019 9:02:39 PM CET

Mack Models
CH , RB , DM , CHN , CL , CT , CV , CX , CXM , LE , MR , RD

Mack Model

** SOLUTION **
Title

V-MAC III Engine Cranks But No Start

Cause

Service Engineering has seen E-Tech (V-MAC III) engine-cranks-but-no-start
conditions that can result from a variety of electrical circumstances.

Soluti

1. INTRODUCTION

on
Service Engineering has seen E-Tech (V-MAC III) engine-cranks-but-no-start conditions that can result from
a variety of electrical circumstances. For an E-Tech engine (V-MAC III) to have the ability to start, the
following conditions must exist:
the fuel supply gallery pressure must be approximately 90 PSI;
the engine sleep mode CDP engine control parameter must be programmed to No;
the V-MAC modules (VECU & EECU) must power up and down in the correct sequence (VJ3-13
power relay control);
the V-MAC modules must be able to communicate on either the J1939 or J1587 data link while the
engine is cranking;
the supply voltage (EJ2-10, EJ2-22, EJ2-41) to the EECU must not fall below 6 volts while the engine
is cranking. Test must be performed with an oscilloscope. A digital voltmeter will not capture the
very rapid voltage fluctuations.
the engine speed must measure a steady result between 150 and 200 RPM while the engine is cranking.

This engine-cranks-but-no-start condition has resulted from any of the following
electrical problems:
the engine sleep mode is programmed to yes;
after an engine shutdown request has be satisfied (after the key is cycled off and the engine has
shutdown), the VECU (step 4) does not de-energize the power relays. This is a power up/down
sequence problem that results from a defective VECU;
greased power relay contacts can also result in a improper powering up sequence. There must be no
grease on the power relay contacts;
the black VECU connector (VJ3) and terminals are improperly assembled. This will inhibit the VECU
to EECU communications;
the Cab harness is entangled with the clutch pedal linkage. This can cause a multitude of open or short
circuits that will inhibit the VECU to EECU communications.
the gray engine/transmission transition (interface) connector and terminals are improperly
assembled. This will inhibit the VECU to EECU communications and or EECU power supply;
for conventional models, the EPDM fuse 40 wiring and terminal connections are not electrically tight.
This will inhibit the EECU power supply.
Batteries must be able to pass an electrical load test.
Starter motor amperage draw is within manufacturer’s specifications.

2. DIAGNOSTICS
This diagnostic procedure assumes that adequate cranking fuel pressure has been established,
there is no severe mechanical engine damage (bent valves), and there are no fault codes logged on
either the VECU or EECU.
As necessary, perform the following steps in descending order. Conduct the necessary corrective actions to
get the results expected for normal conditions. If necessary, proceed to the next step.

2.1 Visual Inspection
First, this diagnostic procedure conducts a detailed visual inspection of all the relays, connectors and terminals
that link the V-MAC power, ground, and communication lines between the Cab Harness, Transmission
Harness and Engine Harness.
Disconnect the following connectors and visually inspect them for corrosion, loose connections, and/or
improper assembly:
EJ1 connector (at the front end of the EECU);

EJ2 connector (at the rear end of the EECU);
Engine/Transmission transition connector (gray 15-way, left side of flywheel housing);
J1939 3-Way Deutsch connector(s);
for conventional models, Engine Power Distribution Module (EPDM)/Transmission connector (gray
12-way, below right side of EPDM);
for conventional models, EPDM fuse 40 terminals and wiring (inspect from the back side the EPDM);
Cab/Transmission Bulkhead connector (23-way for conventional models, and 31-way for COE
models);
Battery power supply ring terminals at the starter relay and starter solenoid;
Battery ground return ring terminals at and the 135 ampere circuit breaker;
Electrical Equipment Panel power relays and fuse 16 (and fuse 40 for COE models) terminals;
VJ3 Connector (black VECU connector).

2.2 E-Tech Engine Sensor & Flywheel & Cam Gear Timing Checks.
Disconnect the Flywheel Sensor from the engine harness, crank engine for up to 10 seconds to see if engine
will start using only Engine Position Sensor as an input to the V-MAC module and log a code 3-2 for the
Flywheel Sensor. Switch off ignition and reconnect the Flywheel Sensor to the engine harness.
Disconnect the Engine Position Sensor from the engine harness, crank the engine for up to 10 seconds to see if
the engine will start using only the Flywheel Sensor as an input to the V-MAC module and log a code 3-4 for
the Engine Position Sensor. Switch off ignition and reconnect the Engine Position Sensor to the engine
harness.
If the engine is able to start and run on only one of either of the two sensors proceed with the checks of the
Flywheel and the Cam Gear. Perform both checks to ensure accurate diagnosis.
2.2.1 Flywheel Check

Using the TC mark on the flywheel, set the engine to TDC on #1 cylinder, put a temporary chalk,
grease pencil or paint mark as a reference point on the bell housing casing access hole that will
indicate the centerline of any one of the ring gear teeth.
Turn the engine in the REVERSE of engine rotation exactly 61½ teeth using the reference point on
the bell housing casing access hole. The centerline between the two missing teeth on the flywheel ring
gear should be aligned in the center of the flywheel sensor hole.

NOTE: If the centerline of the two missing teeth on the flywheel ring gear is not aligned in the center of the
flywheel sensor hole, the ring gear has slipped from its original position and the flywheel/ring gear assembly
will need to be replaced as a unit.
2.2.2 Cam Gear Check
With the engine position unchanged from the test in step 2 of the Flywheel Check above, mark a 2nd
reference point on the bell housing casing access hole that indicates the centerline of another of the
ring gear teeth.
Turn the engine in the normal FORWARD engine rotation exactly 34¼ teeth. The cam gear timing
hole should be in the center of the hole for the engine position sensor located in the timing gear cover.
NOTE: If the sensor hole in the cam gear face is not on the center line of the hole for the engine position
sensor, the cam timing to the crankshaft has changed and has to corrected.
Continue to turn the engine in normal FORWARD rotation 9 ¾ more teeth. The second hole in the
cam gear should align in the center of the timing gear cover sensor hole.
NOTE: If the cam to crankshaft timing is suspected to be incorrect, perform the cam timing check described
in the E-Tech Engine Service Manual 5-106 (on CD #1).

2.2.3 Off-Engine Flywheel Check
The number of teeth on the flywheel should be 117.
Using a straight edge, align the crankshaft dowel pin and pilot bearing to find the center of the
flywheel. Once the straight edge is aligned, count the number of teeth on the ring gear from the two
cut-out teeth to the straight edge and this distance should represent exactly 9 teeth
If you encounter more or less than 9 teeth after counting, the ring gear has slipped on the flywheel and
the flywheel will need to be replaced.

2.3 VECU & EECU Communication Test
Second, using the fault logging capacity of the VECU and EECU, the V-MAC power up and down sequence,
and the VECU to EECU communication lines are tested.
2.3.1 Power Relay Cycle Down Test
With the key cycled Off and the power relays deactivated, measure the voltage at fuses 16 and 40. Both
measurements should be zero. If either measurement reads 12 volts, a power relay is stuck closed or the VJ313, VJ3-17, or 40-A circuit is shorted high.
2.3.2 Power Relay and Ignition Test

With the key cycled On and with the engine cranking, measure the voltage at the VECU pins VJ1-1 (ignition)
and VJ3-13 (power relay). Both measurements must be 10.5 volts or greater. If either measurement is below
7 volts, the switched or clean power is shorting low or open.
2.3.3 Switched Power Test
With the key cycled On and with the engine cranking, measure the voltage at fuses 16 and 40. Both
measurements must be 12 volts. If either measurement is below 7 volts, the switched or clean power is
shorting low or open.
2.3.4 ECU Fault Logging J1939 Test
Remove the ABS fuses (for most cases, 13, 14, and 29).
Remove fuse 16, crank the engine, then check the fault table for logged faults.
By powering up the EECU only, the 6-3, 6-4, and 6-5 J1939 and J1587 fault codes will be logged on
the EECU. If these codes (in any combination) are not logged on the EECU, then this module is not
powering up.
Disconnect EJ2 from the Engine ECU. Then, while the engine is cranking, measure the voltage
between terminals EJ2-10 (high) and EJ2-12 (low), EJ2-22 (high) and EJ2-24 (low), and EJ2-41
(high) and EJ2-43 (low) at the EJ2 connector. If the voltage measure is below 7 volts, the switched or
clean power is shorting low or open.
NOTE: To eliminate power relay 3, remove power relay 3 and install a jumper wire between terminals 30 and
87.
Install fuse 16, remove fuse 40, crank the engine, then check the fault table for logged faults.
By powering up the VECU only, while the engine is cranking, the electronic malfunction light will
illuminate and a 6-4 J1939 fault will be logged on the fault table. If this code is not logged on the
VECU, this module is not powering up.
With the VJ3 connector installed on the Vehicle ECU and while the engine is cranking, measure the
voltage between terminals VJ3-17 (high) and VJ3-18 (low) at the VJ3 connector. If the voltage
measure is below 7 volts, the switched or clean power is shorting low or open. This test can also be
performed with the VJ3 connector disconnected. However, you must jump terminals C and D at the
diagnostic connector, which will energize circuit VJ3-13 and the power relays.
NOTE: To eliminate power relay 1 (or power relay 2 for CH/CL and R Series with the Delphi cab
harness), remove power relay 1 (or 2) and install a jumper wire between terminals 30 and 87.
IMPORTANT: IF THE MALFUNCTION LIGHT IS ILLUMINATED AND 6-4 and/or 6-3 BLINK
CODE IS FLASHED, THE EECU IS NOT POWERING CORRECTLY. TO INSURE THAT THE
EECU IS GETTING ADEQUATE POWER, DO THE FOLLOWING:
Make up a jumper harness, see Figure 1.

Disconnect the gray 12-way Deutsch connector from between the EPDM and the Transmission
harness.
Attach the jumper harness between the Transmission harness gray 12-way Deutsch connector and the
battery side of the starter relay. See Figure 1.
Cycle the key and start the engine.
If the engine starts and the malfunction light goes out and the #3 power relay circuitry is working (see
above), then there is a problem inside the EPDM harness.
If necessary, replace the EPDM harness.

2.4 Engine Speed Signal Input Test
Third, using the fault logging capacity of the VECU and EECU, the engine speed signal inputs to the EECU
are tested.
2.4.1 Engine Speed Cranking RPM Test

Install fuse 40.
Using Service Diagnostics software, monitor the engine speed while the engine is cranking.
Depending on the battery state of charge, the cranking engine speed should measure between 150 to
200 RPMs. If there is no engine speed measured or an NA is recorded, either both the engine speed
sensors are out of adjustment or the engine ECU is not powering up correctly.
NOTE: If an NA or no engine coolant temperature and/or no intake manifold temperature are detected with
monitor parameters, the VECU is not communicating with the EECU. This can be the result of the EECU not
powering up correctly.

2.4.2 Engine Speed Fault Code Test

Test the response of the engine speed and position sensors.
Disconnect the engine speed sensor connector, crank the engine, then check the fault table. By
cranking the engine with the engine position sensor input only, the 3-2 engine speed sensor fault code
will be logged on the EECU. If the 3-2 fault is not logged, the EECU is not seeing the engine position
sensor input.
Connect the engine speed sensor connector.
Disconnect the engine position sensor connector, crank the engine, then check the fault table. By
cranking the engine with the engine speed sensor input only, the 3-4 engine position sensor fault code
will be logged on the EECU. If the 3-4 fault is not logged, the EECU is not seeing the engine speed
sensor input.
2.5 EECU EUP Output Test
Fourth, the engine ECU EUP output signals are tested.
Measure the voltage drop across an EUP as the engine is cranking. If the EECU is trying to energize
the solenoid, a small voltage reading will be measured (0.12 volts AC or 0.016 DC). If the EECU is
powering up correctly, the VECU is not in sleep mode, and there is no measurable voltage drop across
any EUP solenoid, substitute a known good EECU and VECU.
At this point, if no results have been achieved, complete the following chart and contact Service
Engineering.

Dealer
Code

Technician

Model

Serial #
Test

Test to perform

Rang

Result

e
EECU
:
Softw

Datafile

VECU:

Datafile

Software

are
Introduction – preliminary checks
1.

Record logged codes, identify
EECU codes vs. VECU codes

2.

Engine starts with Cam sensor disconnected

3.

Engine starts with Flywheel sensor disconnected

4.

Fuel supply pressure

Yes /
No
Yes /
No
Appr
ox.
90PSI
Yes /

5.

Engine sleep mode programmed to “No”

6.

Power relays de-energize the VECU. (Step4)

7.

8.

9.

10.

11.

12.

13.

14.

No
Yes /
No

Codes EECU logged w/ fuse 16 removed and
engine cranking with key on
Codes VECU logged w/ fuse 40 removed and
engine cranking with key on
Batt volts to EJ2-10,22,41 greater than 6V (test
to be performed with oscilloscope not DVOM)

6.5V
to
11.5V

Fuse panel terminals are grease free and each

Yes /

applies secure grip to power relays

No

Fuse panel terminals are grease free and each

Yes /

applies secure grip to all fuses

No

EPDM panel terminals are grease free and each

Yes /

applies secure grip to fuse 40

No

Batteries pass an electrical load test

(Refer to

Yes /

manufactures Load Testing specifications)

No

Cab harness is not entangled in the foot pedal

Yes /

mechanisms

No

Starter motor amperage draw test compares to
15.

likewise application. (Compare test results to

Yes /

similarly configured truck ie. Engine,

No

temperature, starter motor, batteries etc.)
Visual Inspection – disconnect & inspect for corroded, loose, damaged & improperly assembled
16.

EJ1 connector

17.

EJ2 connector

18.

VJ1 VJ2 VJ3 connectors

19.

Engine / Transmission Transition connector

20.

J1939 connectors

21.

22.

Yes /
No
Yes /
No
Yes /
No
Yes /
No
Yes /
No

EPDM/Transmission connector. Grey 12-way

Yes /

Conventional Models

No

EPDM fuse 40 terminals and wiring

Yes /

Conventional Models

No

23.

24.

25.

26.

Cab/Transmission bulkhead connector (23-way

Yes /

Conventional Models) (31-way COE Models)

No

Battery power supply terminals at battery

Yes /
No

Battery power supply terminals at starter

Yes /

solenoid

No

Battery power supply terminals at starter relay

Yes /
No

VECU & EECU Communication Test
27.

28.

29.

Solution visibility

Power relays deactivate with key cycled OFF

Yes
No

VJ1-1 & VJ3-13 have 10.5V or greater with key

Yes

on and engine cranking

No

Fuses 16 & 40 have 10.5V or greater with key

Yes

on and engine cranking

No

Dealer distribution

Function(s)/component(s) affected
Function affected

EECU , MID 144 – VECU , VECU , VMAC , wiring harness , starting

Function Group
Function Group

16 electrical standard parts , 21 engine , 23 fuel system, excluding gas propulsion , 31
1 battery; energy storage system , 367 electronic components

Customer effect
Main customer effect

power supply , stop/start

Conditions
Vehicle operating mode
Frequency of occurrence of
problem

on start-up , when stationary
random

Administration
Author

A241298

Dealer ID

A241298

Last modified by

A241298

Creation date

20-12-2018 16:12

Date of last update

20-12-2018 17:12

Status

Published