This page contains info courtesy of Eric Giordano. This page includes an easy into follow set of diagnostics to your early version 4.0L Jeep Cherokee with RENIX based engines & detectors. JabaThaHut supplied this information and was posted on Jeeps Unlimited. This information was edited to add my images and info and is provided with his permission. Because they occur, tidbits are added, but the majority of the page is the work of Eric. – Here is something I wrote a while up. To test, use a high volt ohmmeter. Resistance should be less than one thousand ohms with a WARM engine will be 1, 600 ohms).
> What does it do? Adjusts the injector pulse widths. Compensates for gas condensation in intake manifold. Controls motor warm-up idle speed. The EGR valve solenoid to avoid flow of vacuum. Update: Basically – by supplying a ground circuit which the computer uses to ascertain how much fuel the engine requires this detector works.
The resistance of the sensor is read by the ECU which in turn adjusts the air\/fuel ratio as close to 14.7: 1 as possible. For mobile car wash service in Birmingham, when a coolant temperature sensor fails the high \/ infinite resisitance it will cause the ECU to falsely read the max low temperature of -40 degrees F.
The ECU tells the injectors into enrichen the fuel mix since it thinks when it is in factn’t the temp is cold. A short to ground might Cause a no immunity fault causing the ECU to believe the coolant air temperatures was extremely hot and rests on the fuel mix.
Unlike late HO engines, RENIX engines do NOT have a combined coolant temperatures sensor that also feeds the gauge. RENIX vehicles use a SEPARATE detector located on the back 50% of the head, driver side – Resistance chart to both Coolant Temperature Sensor – -and-. Manifold Air Temperature – Coolant Temperature and Manifold Air Temperature Sensor Resistance Values – Approximate immunity your metre should show at the temperatures shown in the chart.
NO immunity indicates a short to earth – can function as sensor, but will most likely be a wire where that the insulation has been abraded. INFINITE resistance indicates an open broken circuit. Can either be a broken wire or a bad detector. Degrees Fahrenheit – Degrees Celcius – Resistance in Ohm – 0 – -18 – 25, 000 – 40 – 4 – 7, 500 – Manifold Air Temperature Sensor – Installed in that the top of that the intake manifold.