Question about 2002 Subaru Forester
What is the resistance range. Have dtc P0420
What scantool do you own ? lets just keep it simple (for now) you should be looking at "ECT temp " .... also P0420 has nothing to do with a ECT sensor
Posted on Jun 05, 2014
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Posted on Jan 02, 2017
that code is saying you have a problem with that system. if you go to autozone thay can print that code out for that tells you what to check. other then that you may need to get it diagnosed by a professional
Posted on Nov 23, 2009
SOURCE: P0420 on a 2000 Subaru Forester
P0420 is one of two things, it is either a catalyst failure (below threshold) or rear lambda.
The rear lambda should have a steady waveform when the engine is running if not then P0420 will be stored.
Cats and lambdas are very common on Subaru.
As the car is older than 2001 it does not come under R103 regulations therefore you could cut out the old cat and replace with a Carsound (Magnaflow) universal bullet. That will save you £££
The Subaru lambdas are now available aftermarket so try a motor factor, not the dealers.
If UK email me for info on where to purchase any of the above.
Posted on Dec 03, 2009
It usually take a few days and a few dozen miles for all the rediness monitors to reset. The car must go through different types of drive patterns during this time, including stop and go traffic, steady highway driving, a few quick accelerations, and quick stops.
Posted on Feb 26, 2010
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Aug 19, 2016 | Cars & Trucks
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The control module detects a temperature difference between the ECT sensor and the IAT sensor of more than 15°C (27°F) and the time elapsed cranking the engine without starting is more than 5 seconds.
The control module detects a temperature difference between the ECT sensor and the IAT sensor of more than 15°C (27°F). The vehicle must then be driven for 5 minutes over 40 km/h (25 mph). If the IAT sensor temperature decreases more than 5°C (9°F), an engine block heater was detected and the test is aborted. If the IAT sensor temperature does not decrease, an engine block heater was not detected and DTC P0116 will set.
Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor. Engine coolant that is leaking through the sensor will create a high resistance short to ground. This condition results in less voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a warmer ECT.
An IAT sensor that is skewed colder at various ambient temperatures due to greater resistance than is normal will increase the range between these two sensors. Measure and record the resistance of the IAT sensor at various ambient temperatures, then compare those measurements to the Temperature vs Resistance table. Refer to Temperature Versus Resistance .
A slight to moderate resistance in the IAT sensor signal circuit or low reference circuit will increase the range between these two sensors. This condition results in a greater voltage on the IAT sensor signal circuit, which is interpreted by the ECM as a colder IAT.
Feb 08, 2016 | Cars & Trucks
Aug 08, 2015 | Cars & Trucks
A DTC will be set if an abnormal reading occurs, P0116 for sensor performance, P0117 low input or
P0118 for a high input. The coolant temperature sensor temperature reading should closely match the
air charge/manifold temperature reading on a scan tool if the engine has not been run for over an hour.
The sensor circuit can be checked for proper voltage using a voltmeter.
Jun 03, 2015 | Cars & Trucks
Feb 05, 2015 | Subaru Cars & Trucks
The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively low ECT signal voltage, which is a high temperature indication, DTC P1114 sets.
Conditions for Running the DTC
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