Other configurations use an electric water pump to cool the engine’s turbochargers after a hot shutdown. Some cooling systems use electric water pumps to circulate warm coolant through one or more heater cores to keep passengers warm when the engine is shut off. Some cooling systems include features like electronic thermostats or even dual thermostat configurations, all of which are designed to shorten engine warm-up times. On other platforms, water-cooled exhaust manifolds force engines to reach operating temperature within minutes of a cold-soak start. As a result, we might be seeing old-technology components like radiator shutters make a comeback on some vehicle platforms. Modern cooling system design is most often concerned with warming up the engine as quickly as possible and maintaining a constant coolant temperature. So, unless the ECT achieves full operating temperature within a specified length of time, diagnosing an intermittent or random no-code driveability or stalling complaint is nearly impossible. For example, a DTC for a failed oxygen sensor might not be stored if the engine fails to reach operating temperature. While enable criteria might include engine run time, specific system voltage levels, engine load and other operating parameters, most enable criteria will also include engine coolant temperatures. When designing a diagnostic test monitor, automotive engineers create a set of operating conditions (enable criteria) that must exist before the monitor will test the circuit in question. Photo 1: Will this 2002 Toyota 4Runner store DTCs at 178º F coolant temperature? The answer lies with the 4Runner’s DTC enable criteria.
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