Edmunds Answers

Voted Best Answer

  • avatar zaken1 05/01/09 12:46 am PST

    There was a design problem in the emission control system used on OBD 1 (1995 and earlier) Chrysler, Dodge, and Plymouth engines; which would shut off the spark if any of the emission control sensors developed a short. The sensors which can trigger this problem if they become shorted include the throttle position sensor; manifold pressure (MAP) sensor; the coolant temperature sensor for the fuel injection; crankshaft position sensor; air charge temperature sensor; and the heating element in one of the 4 wire heated oxygen sensors.

    Any one of those sensors can shut the spark off if they become shorted. The engine control system was redesigned in 1996 and later OBD II systems to be immune to this problem.

    You could try disconnecting each of those sensors, one by one, and keep testing until you get a spark. Then just replace the sensor that caused the problem. Just in case the computer set a trouble code from the shorted sensor; it would be good insurance to disconnect the battery ground cable for at least 60 seconds, and then reconnect it; before each time you disconnect another sensor to see if you now get a spark.

Answers

  • zaken1 05/01/09 12:46 am PST

    There was a design problem in the emission control system used on OBD 1 (1995 and earlier) Chrysler, Dodge, and Plymouth engines; which would shut off the spark if any of the emission control sensors developed a short. The sensors which can trigger this problem if they become shorted include the throttle position sensor; manifold pressure (MAP) sensor; the coolant temperature sensor for the fuel injection; crankshaft position sensor; air charge temperature sensor; and the heating element in one of the 4 wire heated oxygen sensors.

    Any one of those sensors can shut the spark off if they become shorted. The engine control system was redesigned in 1996 and later OBD II systems to be immune to this problem.

    You could try disconnecting each of those sensors, one by one, and keep testing until you get a spark. Then just replace the sensor that caused the problem. Just in case the computer set a trouble code from the shorted sensor; it would be good insurance to disconnect the battery ground cable for at least 60 seconds, and then reconnect it; before each time you disconnect another sensor to see if you now get a spark.

  • littleredhead 05/01/09 10:51 am PST

    where are the sensors located???

  • zaken1 05/01/09 1:42 pm PST

    I'll give you a general idea of the location of those sensors; but I suggest that you go to Rock Auto's website, at the address referenced below, and look up your truck's year and model in their online catalog. There will be photos of the air charge temperature sensor, oxygen sensor, and throttle position sensor in the "emission" category. And there will be a photo of the coolant temperature sensor in the "cooling system" category. To see these photos; just click on the blue icon with the letter "i" in it, which follows the part number listing for an item.

    The air charge temperature sensor is located in the air filter housing.

    The oxygen sensors are located at different points in the exhaust pipes and manifolds. There may be two, three, or four of them on your truck. Some of them have different numbers of wires in the connectors. The ones which could could create the no spark problem will have four wires.

    The throttle position sensor is located in the throttle body; which is attached to the intake manifold.

    The manifold pressure sensor is probably located on the firewall, or mounted on a bracket somewhere on top of the engine. It will have an electrical plug, and a vacuum hose which comes from the intake manifold.

    I hope this helps. I'm posting a copy of this response in both of the locations where your questions are located; but please heed Steve's instructions about keeping all of your responses in the same thread, by clicking on the "answer this question" button underneath the original question, to post additional responses in the future.

    Source: www.rockauto.com

  • 320000problems 07/24/12 10:08 pm PST

    I completely agree with the one voted best answer, would just like to add, and I know this from experience with my 95 ram 2500 with the 360 V8. The speedometer sensor shares the Signal voltage with those other circuits. Mine shorted to ground and cut the signal voltage to all those sensors and would not create spark. The speed sensor would be located on the driver`s side of the tailshaft of the transmission or transfer case. It will be a 3 wire plug.

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