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Tom, ASE Master Certified
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2007 dodge ram 1500 4x4: 5.7 hemi..my temperature guage

Resolved Question:

I have a 2007 dodge ram 1500 4x4 with a 5.7 hemi. I just recently changed my thermostat because my temperature guage would move a little from the inside of my truck. mainly at higher speeds. If I go 60 mph the temperature will stay were its suppose to be. If I go 75 mph the temperature gauge will move closer to the middle range on the gauge. It can stay idling for ever, not moving, and the gauge want move. The truck has 49,000 miles on it. I bought it used and did a car fax on it. The car fax showed that it sat up for about a year before being bought. Not sure if that would have anything to do with my problem. it doesnt over heat. The temperature guage moves maybe an inch when it does move.
Submitted: 4 years ago.
Category: Dodge
Expert:  Tom replied 4 years ago.

Hello and welcome to JA.

 

Your temp gauge is not hard wired to any sending unit for engine temp. It is a calculated value based on many inputs and it relayed to the instrument cluster via a digital computer message. The gauge reading that you are seeing is a calculated relative position on the scale based on engine load transmission load etc. In other words, your gauge and your engine are operating correctly. As long as your gauge does not run in the red you are fine. If you do have doubts about the actual temp the best thing to do would be to get a scan tool that can read data so that you can compare the readings of the ECT engine coolant temp sensor to your gauge non the dash. Her is the Chrysler service info description of the temp gauge.

 

OPERATION

The engine coolant temperature gauge gives an indication to the vehicle operator of the engine coolant temperature. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) on vehicles equipped with a gasoline engine, or the Engine Control Module (ECM) on vehicles equipped with a diesel engine over the Controller Area Network (CAN) data bus.

The engine coolant temperature gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or START positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the OFF position. The instrument cluster circuitry controls the gauge needle position and provides the following features:

  1. Engine Temperature Message - Each time the cluster receives an electronic engine temperature message from the PCM or ECM indicating the temperature is between the low end of normal [about 54 °C (130 °F) for gasoline engines, or about 60 °C (140 °F) for diesel engines] and the high end of normal [about 122 °C (252 °F) for gasoline engines, or about 116 °C (240 °F) for diesel engines], the gauge needle is moved to the actual relative temperature position on the gauge scale.
  2. Engine Temperature Low Message - Each time the cluster receives an electronic engine temperature message from the PCM or ECM indicating the temperature is below the low end of normal [about 54 °C (130 °F) for gasoline engines, or about 60 °C (140 °F) for diesel engines], the gauge needle is held at the graduation on the far left end of the gauge scale. The gauge needle remains at the low end of the gauge scale until the cluster receives a message from the PCM or ECM indicating the temperature is above about 54 °C (130 °F) for gasoline engines, or about 60 °C (140 °F) for diesel engines, or until the ignition switch is turned to the OFF position, whichever occurs first.
  3. Engine Temperature High Message - Each time the cluster receives three consecutive electronic engine temperature messages from the PCM or ECM indicating the temperature is above about 122 °C (252 °F) for gasoline engines, or about 116 °C (240 °F) for diesel engines, the gauge needle is moved to the red increment or zone at the far right end of gauge scale, the check gauges indicator is illuminated, and a single chime tone is sounded. The gauge needle remains at the high end of the gauge scale and the check gauges indicator remains illuminated until the cluster receives a message from the PCM or ECM indicating that the temperature is below about 122 °C (252 °F) for gasoline engines, or about 116 °C (240 °F) for diesel engines, or until the ignition switch is turned to the OFF position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the check gauges indicator is cycled OFF and then ON again by the appropriate messages from the PCM or ECM.
  4. Communication Error - If the cluster fails to receive an engine temperature message, it will hold the gauge needle at the last indication for about 10 seconds or until the ignition switch is turned to the OFF position, whichever occurs first. After 10 seconds, the cluster will move the gauge needle to the low end of the gauge scale.
  5. Actuator Test - Each time the cluster is put through the actuator test, the engine coolant temperature gauge needle will be swept to several calibration points on the gauge scale in a prescribed sequence in order to confirm the functionality of the gauge and the cluster control circuitry.

The PCM (gasoline engine) or ECM (diesel engine) continually monitors the engine coolant temperature sensor to determine the engine operating temperature. The PCM or ECM then sends the proper messages to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN). For further diagnosis of the engine coolant temperature gauge or the instrument cluster circuitry that controls the gauge. If the instrument cluster turns ON the check gauges indicator due to a high engine temperature gauge reading, it may indicate that the engine or the engine cooling system requires service.

For proper diagnosis of the engine coolant temperature sensor, the PCM, the ECM, the EMIC, the CAN data bus or the electronic communication related to engine coolant temperature gauge operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

Tom, ASE Master Certified
Category: Dodge
Satisfied Customers: 806
Experience: Chrysler Level 3 Technician, Chrysler Training Instructor
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