MACS Monthly Newsletter - 2022 - MAR4

to " better than new " ! All the warnings mentioned in
the first paragraph of this section apply to this option.
SAFETY FIRST!
A failed HV battery is often the deciding factor
when a Hybrid or EV owner decides to upgrade to a
more current or new vehicle. If in reasonable condition
this vehicle is then likely to enter the used vehicle
marketplace. Independent shops are then more
likely to see this vehicle in their service bay.
The instrument cluster warnings, trouble codes
and scan tool data will help to diagnose a failed
High Voltage battery. Aftermarket programs can also
Figure 5: 2014 Infiniti QX60 High Voltage System Failure.
Instrument cluster warnings
Figure 4 notes the HV warning lights available on
our 2008 Toyota Prius (Prius II). Note the " Triangle
of doom. " On this vehicle, this symbol can indicate
different failures, including a High Voltage Battery
problem. Figure 5 shows our Infiniti QX60 has recognized
a high voltage system failure by turning on
the " CAR! " light.
Experience has shown that the meaning of warning
lights on different years, makes and models can
vary dramatically. As a first step, dig out the owner's
manual to help determine the possible meaning of
the warning lamp. If various faults can illuminate
the lamp, a scan tool and service information will be
helpful to isolate the system responsible for turning
the lamp on.
Engine cooling systems
Hybrid vehicles usually employ two cooling sysFigure
4: 2008 Toyota Prius driver warnings.
be very handy. Figure 3 is a screen shot from my device
while running the Dr. Prius app for Toyota and
Lexus vehicles! You can easily see the problem battery
blocks on the simple bar graph. The two weak
block bars will even turn red when the failure is severe
which makes it an excellent sales tool. You can
find it in the app store or go to www.priusapp.com
to research the app and get more information on
Lithium upgrades.
March 2022
4
tems. The first, for the ICE, is typical but with a few
modifications, and may depend on the manufacturer.
For example, older Toyota Prius systems employ
a coolant " heat storage tank, " an electric pump to
flow water from the tank and a coolant control valve
to direct flow to the proper place at the proper time.
Have a look at Figure 6. When looking at the actual
vehicle, there are so many coolant hoses it can get
confusing. This diagram will help to visualise and
identify coolant flow.
In the diagram, hashed arrows signify " normal "
coolant flow, and solid arrows signify " Preheat "
coolant flow. Components of the " Preheat " system
include the ECM, Coolant Heat Storage Tank (CHS
Tank), CHS Water Pump, CHS Outlet Temperature
Sensor and the Water Valve.
MACS Service Reports
Mitchell Pro-Demand
Mike Bailey
http://www.priusapp.com
MACS Monthly Newsletter - 2022

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