MACS Service Reports - 2015 - JUL7

still work, but will likely set U-Codes and act up
in the most unusual and intermittent ways. In the
Chrysler and Mercedes CAN systems, since the Diagnostic CAN C only goes from the gateway to the
DLC, a single 60 ohm resistor is used internal to
the gateway module for HS CAN bus termination
(Figure 14).

Dave Hobbs

What Can My Scan Tool Do?

Dave Hobbs

Fiat Chrysler Automobiles

Figure 11 The SAE J1850 for Ford means a back up circuit that is the mirror image of the other. This provides for a more robust communications
network. Both pins 2 and 10 at the DLC rest at .5 volts and either go up
to +5 volts or down to -5 volts.

Figure 12: Dual tracing HS 2-wire CAN bus shows a normal pattern for
an active bus. Note the shift from 2.5 to 3.5 volts on CAN HS High and
shift down from 2.5 volts to 1.5 volts on CAN HS Low. The time base is
set to 10 microseconds per division. CAN is fast!

Figure 14 This Chrysler CAN bus circuit is similar to Mercedes in regards to using a gateway module to connect a dedicated "Diagnostic" bus
(CAN C Diagnostic) from the gateway to the DLC. Notice the twisted
pair wiring used on the high speed CAN circuits and the single 60 ohm
termination resistor in the CAN C Diagnostic circuit.

Fiat Chrysler Automobiles

TECH TIP:
When more than one bus is having problems with data corruption or intermittent
shorting, always check the module that is
common to both busses - the gateway!
Depending on your particular scan tool, besides simply attempting to pull DTCs or Data PIDs from a module on the bus,
some aftermarket factory level scan tools such as Ease, Blue
Streak, Auto Enginuity and a few other PC based tools will allow you to do a complete vehicle DTC scan. Many of the newer
scan tools that do this will have a line of data on the tool telling
you which module it's attempting to communicate with and
what the result was of that attempt prior to going on to the next
module it initiates communications with. If you see a failed attempt at communications on a particular module, see if the vehi

Figure 13: All CAN data bus equipped vehicles can have their termination resistors tested with an ohmmeter applied between pins 6 and 14 of
the DLC, or at any other point between CAN HS- and CAN HS+. Two
120 ohm resistors wired in parallel equal 60 ohms. If you measure 120
ohms, one of these resistors is missing. On this Chrysler, the TIPM is the
gateway module. A TIPM is an FCM (Front Control Module / BCM) and
relay center / fuse panel (Integrated Power Module) combined into 1 unit.

July 2015

7

MACS Service Reports



Table of Contents for the Digital Edition of MACS Service Reports - 2015

MACS Service Reports - 2015 - JAN1
MACS Service Reports - 2015 - JAN2
MACS Service Reports - 2015 - JAN3
MACS Service Reports - 2015 - JAN4
MACS Service Reports - 2015 - JAN5
MACS Service Reports - 2015 - JAN6
MACS Service Reports - 2015 - JAN7
MACS Service Reports - 2015 - JAN8
MACS Service Reports - 2015 - FEB1
MACS Service Reports - 2015 - FEB2
MACS Service Reports - 2015 - FEB3
MACS Service Reports - 2015 - FEB4
MACS Service Reports - 2015 - FEB5
MACS Service Reports - 2015 - FEB6
MACS Service Reports - 2015 - FEB7
MACS Service Reports - 2015 - FEB8
MACS Service Reports - 2015 - MAR1
MACS Service Reports - 2015 - MAR2
MACS Service Reports - 2015 - MAR3
MACS Service Reports - 2015 - MAR4
MACS Service Reports - 2015 - MAR5
MACS Service Reports - 2015 - MAR6
MACS Service Reports - 2015 - MAR7
MACS Service Reports - 2015 - MAR8
MACS Service Reports - 2015 - APR1
MACS Service Reports - 2015 - APR2
MACS Service Reports - 2015 - APR3
MACS Service Reports - 2015 - APR4
MACS Service Reports - 2015 - APR5
MACS Service Reports - 2015 - APR6
MACS Service Reports - 2015 - APR7
MACS Service Reports - 2015 - APR8
MACS Service Reports - 2015 - MAY1
MACS Service Reports - 2015 - MAY2
MACS Service Reports - 2015 - MAY3
MACS Service Reports - 2015 - MAY4
MACS Service Reports - 2015 - MAY5
MACS Service Reports - 2015 - MAY6
MACS Service Reports - 2015 - MAY7
MACS Service Reports - 2015 - MAY8
MACS Service Reports - 2015 - JUN1
MACS Service Reports - 2015 - JUN2
MACS Service Reports - 2015 - JUN3
MACS Service Reports - 2015 - JUN4
MACS Service Reports - 2015 - JUN5
MACS Service Reports - 2015 - JUN6
MACS Service Reports - 2015 - JUN7
MACS Service Reports - 2015 - JUN8
MACS Service Reports - 2015 - JUL1
MACS Service Reports - 2015 - JUL2
MACS Service Reports - 2015 - JUL3
MACS Service Reports - 2015 - JUL4
MACS Service Reports - 2015 - JUL5
MACS Service Reports - 2015 - JUL6
MACS Service Reports - 2015 - JUL7
MACS Service Reports - 2015 - JUL8
MACS Service Reports - 2015 - AUG1
MACS Service Reports - 2015 - AUG2
MACS Service Reports - 2015 - AUG3
MACS Service Reports - 2015 - AUG4
MACS Service Reports - 2015 - AUG5
MACS Service Reports - 2015 - AUG6
MACS Service Reports - 2015 - AUG7
MACS Service Reports - 2015 - AUG8
MACS Service Reports - 2015 - SEP1
MACS Service Reports - 2015 - SEP2
MACS Service Reports - 2015 - SEP3
MACS Service Reports - 2015 - SEP4
MACS Service Reports - 2015 - SEP5
MACS Service Reports - 2015 - SEP6
MACS Service Reports - 2015 - SEP6
MACS Service Reports - 2015 - SEP7
MACS Service Reports - 2015 - OCT1
MACS Service Reports - 2015 - OCT2
MACS Service Reports - 2015 - OCT3
MACS Service Reports - 2015 - OCT4
MACS Service Reports - 2015 - OCT5
MACS Service Reports - 2015 - OCT6
MACS Service Reports - 2015 - OCT7
MACS Service Reports - 2015 - OCT8
MACS Service Reports - 2015 - NOV1
MACS Service Reports - 2015 - NOV2
MACS Service Reports - 2015 - NOV3
MACS Service Reports - 2015 - NOV4
MACS Service Reports - 2015 - NOV5
MACS Service Reports - 2015 - NOV6
MACS Service Reports - 2015 - NOV7
MACS Service Reports - 2015 - NOV8
MACS Service Reports - 2015 - DEC1
MACS Service Reports - 2015 - DEC2
MACS Service Reports - 2015 - DEC3
MACS Service Reports - 2015 - DEC4
MACS Service Reports - 2015 - DEC5
MACS Service Reports - 2015 - DEC6
MACS Service Reports - 2015 - DEC7
MACS Service Reports - 2015 - DEC8
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