High Idle / MPG Fooler Diagnostic
I know a bunch of you have either built your own high idle mod or purchased one through Diesel Auto Power. But I know a few of you have had some diagnostic problems or have had issues after installing. Well this little write up should walk you through most of it ad figure out what is going on.
Ok let get down to tools… You’ll need a DVM (Digital Volt Meter) set on ohms.
Now lets start with the ECT (Engine Coolant Temperature) fooler…
Now with the female plug which is the plug that hooks to the ECM (Engine Control Module) we want to measure the ohms at this plug with the fooler in the ON position. It should read 3.3K ohms. If its open check the other male connector and see if the values shows if it does you have your plug sex backward and need to be traded. If open on both test check the wiring for breaks or toggle the fooler switch the other direction.
Now for the IAT (Intake Air Temperature) Fooler
Now lets test the normal mode. This is the normal pass through mode without the foolers…
Now here in the normal mode both IAT (Intake air Temperature) and ECT (Engine Coolant Temperature Sensor) fooler should operate the same with 0 Ohms between RED and BLUE arrows. Now you might see a OPEN at this point but trade pins on one plug and see if you get 0 ohm… There should be a pair of 0 ohm wires coming and going probing from the ECM to the sensor plugs. If this remains OPEN double check your fooler switch and make sure its in the OFF position. Now if it continues to be a open there is a open wire somewhere.
Now for error codes with High Idle Mod in place.
IAT Fooler Error Codes
P0112 means you most likely got a short to ground double check your wiring for cuts, shorts, etc.
P0113 means you got a OPEN wire in the fooler go back and test the bypass mode for problems.
In any case remove the IAT (Intake Air Temperature) fooler reset the code and take for a short test drive if the code returns the sensor is at fault.
ECT Fooler Error Codes
P0117 means you most likely got a short to ground double check your wiring for cuts, shorts, etc.
P0118 means you got a OPEN wire in the fooler go back and test the bypass mode for problems.
In any case remove the ECT (Engine Coolant temperature) fooler reset the code and take for a short test drive if the code returns the sensor is at fault.
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