But was obviously running extremely rough, probably 2 – 3 cylinders. Maybe there is a gasket leak, but in the time I drove it home it fouled the plugs, causing no combustion and there for no steam? Like I said before, after it cooled down I was able to drive it home with no temp problems. Right after it cooled down (bout 13 or 14 hours), I started it and there was alot of steam coming from the exaust. Could the the circuit failure described in the code listing indicate fairly certainly that it does have some kind of plug problem. Thank you LanEvoX, college man, and of course Eric the main man! I Generally learn by doing, but with having to take valves off and such for the gasket, I would very much prefer a step by step plan. Any guides on either Gasket replacement, or Plug replacement for this truck would be great. I tried finding a PDF of a service manual, but I’m very sure its not OEM, and is really hard to follow. The plugs are so burried under the fuel injectors and valve cover that I can’t even see where they meet into the head.Īny help would be very much appreciated. But it definately sounds like its running on no more than 3 cylinders, maybe even just 2 :ohmy: Also, I need to know how to tell what wires are for what cyl, as this 4 cyl has 8 wires and 8 plugs. I will try to attach a picture of the Code read out, and see what you guys think. Prefferably the cheaper and quicker of the 2. These only showed up after badly over heating, so its either head gasket or head leaking, or badly fowled plugs or something. This will give you quick way to determine if you have a sensor issue or a wiring issue.I have some OBD 1 codes I could really use some help on. If in doubt, measure the sensor’s resistance and compare the resistance to both a scan tool PID and a temperature laser reading. Likewise, after a 30 minute drive, you know you are supposed to be in the hot range. It all depends on what range you were in, so if you were checking the sensor immediately after a cold soak start up, you would know you are suppose to be in the cold range. A 3.07V reading could mean 110 degrees C (230☏), while 3.26V could mean 20 degrees C (68 degrees F). Looking at the chart in Figure 4, you will notice that there is the potential for confusion outside of the overlap zone. It is in this range a technician can become confused watching a sudden voltage change from 3.71V to 0.60V. During the overlap stage from one resistor to another, computer programming watches and determines which value is correct (the cold end or the hot end). With two resistors, the sensor can provide a constant linear voltage representation across a wide range of temperatures. In other words, for this sensor to have a range of -40 degrees C (-40 degrees F) to a high 260 degrees C (500 degrees F), two resistors are required. For example, at 90 degrees C (194 degrees F), the voltage could read either 0.060V or 3.71V.” Note the temperature to voltage, “Overlap zone.” Within this zone, it is possible to have either a “Cold end” or "Hot end” voltage at the same temperature. A graph showing temperature switching from the “Cold end” to the “Hot End” line, with increasing temperature and back with decreasing temperature is included. "To cover the entire temperature range of both the CHT and ECT sensors, the PCM has a dual switching resistor circuit on the CHT input (5V line). “On applications that do not use an engine coolant temperature (ECT) sensor, the CHT sensor is used to determine the engine coolant temperature," Ford notes. The PCM receives the various voltage signals and equates it to a temperature value. A basic description of the sensor is that it is a thermistor device in which resistance changes with temperature.Īs the temperature increases, the resistance decreases causing a voltage drop to occur on the 5V signal wire. A 2-wire sensor to infer coolant temperature. Monitoring its voltage change without a basic understanding of its operation can be confusing.Īccording to Ford, this is a primary input in the PCM’s strategy to control Torque Converter Clutch (TCC) operation. In fact it is quite a sophisticated little system. Some of the information may no longer be relevant, so please use it at your discretion.įord’s CHT sensor signal is not a typical 5 volt linear signal. Editor's Note: This article was orginally published June 10, 2013.
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