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Post by yjsaabman on Mar 15, 2007 17:53:39 GMT -5
The values stated in this thread are based on a 5V refference system, which is the standard system Chrysler uses.
Most of the sensors involved will have 3 leads, consisting of a ground, a 5V refference signal, and the signal line to the ECM. Simply probing the plug to the sensor with a standard DVOM (Dual range Volt Ohm Meter) on the proper DC scale will determine which wire is which. These should be probed with the ignition in the "run" position to determine location, and in some cases tested with the engine running. Be very careful of moving parts, like the fan and acc. belts while working around a running engine!! Use the DVOM to probe the signal wire to check for proper function.
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Post by yjsaabman on Mar 15, 2007 17:54:07 GMT -5
Start off with some coolant sensor values:
Cold (open loop): *F Volts -20 4.7 -10 4.57 0 4.45 10 4.30 20 4.10 30 3.90 40 3.60 50 3.30 60 3.00 70 2.75 80 2.44 90 2.15 100 1.83 110 1.57 120 1.25
Hot (closed loop): *F Volts 110 4.2 120 4.10 130 4.00 140 3.60 150 3.40 160 3.20 170 3.02 180 2.80 190 2.60 200 2.40 210 2.20 220 2.00 230 1.80 240 1.62 250 1.45
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Post by yjsaabman on Mar 15, 2007 17:54:25 GMT -5
TPS: Throttle Position Sensor is located on the side of the throttle body, opposite where the throttle cable attatches. With the key in the "On" or "Run" position, probe the 3 wire connector, using a standard DVOM, to locate the signal wire. TPS signal voltage should be low with the throttle closed, and gradually and smoothly increase as the throttle is opened. Watch the DVOM display while cycling the throttle open, then closed again. Look for dips or spikes, as these indicate an issue with the sensor. If you notice ANY abnormalities in the signal from the sensor it is faulty and it should be replaced.
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Post by yjsaabman on Mar 15, 2007 17:54:51 GMT -5
Crank Postion Sensor (Commonly referred to as "CPS", DC denotes it "CKP." We'll stick with the more common CPS.)
The CPS is located on the left side of the bellhousing, towards the top. Depending on model and engine, the CPS may be held on with one or two bolts. The CPS is ahall-effect type induction sensor, like those found in modern day electrinic distributors. It uses keyways or slots in the flywheel to provide engine speed and crankshaft position information to the engine computer. The computer, in turn, uses this information to time fuel delivery and ignition timing. The following is a quote from a Chrysler training manual: "Without this signal, the vehicle will not start. In these cases, the Malfunction Indicator Lamp (MIL) will not illuminate because the engine will not reach its "start-to-run" rpm."
CPS failure is fairly common in the Jeep 4.0L engine. It sometimes occurs while driving, causing the engine to shut down, and not to re-start. The simplest way to diagnose the problem is to pull the coil wire off the distributor and ground it to the engine. Then have some crank the engine while you watch for spark. Lack of spark is a good indication that it's the CPS. Sometimes simply dis-connecting and re-connecting the sensor will allow the vehicle to run again for a brief period.
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