Could be the gauge also , which means the instrument cluster would have to be repaced . Rather then playing around with the coolant temp sensor an wiring diagrams , have it checked for code's . Your vehicle has a cylinder head temp sensor .(CHT)
Principles of Operation
The Expedition and Navigator instrument clusters are configurable, hybrid electronic clusters (HEC) that contain a microprocessor, gauges, indicator lamps, and internal circuitry. The instrument cluster is non-repairable at the dealership level with the exception of the warning indicator bulbs on the Expedition only and the instrument cluster lens on both the Expedition and Navigator clusters. The instrument cluster utilizes hardwired circuitry, the standard corporate protocol (SCP), and universal asynchronous receiver-transmitter (UART)-based protocol (UBP) communication networks. Communication using the SCP network transmits and receives data between the instrument cluster, the powertrain control module (PCM), and the anti-lock brake system/traction control/integrated vehicle dynamics (ABS/TC/IVD) module. Communication using the UBP network utilizes data transmitted and received by the instrument cluster and the four-wheel drive control module, power liftgate module (Navigator only), parking aid module, air suspension module, vehicle security module, driver seat module and the electronic air temperature control (EATC). For additional information regarding the SCP and UBP communication networks, refer to Section 418-00 .
It is very important to understand:
- where the input originates from.
- all the information necessary in order for a feature to operate.
- which module(s) receive(s) the input or command message.
- Does the module which received the input control the output of the feature, or does it output a message over the SCP or UBP network to another module?
- which module controls the output of the feature.
- Temperature Gauge
The PCM receives the engine coolant temperature status through hardwired circuitry to the engine coolant temperature (ECT) sensor. The instrument cluster receives the engine coolant temperature data from the PCM through the SCP communication network. The instrument cluster microprocessor monitors the engine coolant temperature data received from the PCM and commands the temperature gauge indication with a corresponding movement of the pointer.
- Incorrect temperature gauge indication
- Cylinder head temperature sensor.
- Powertrain control module (PCM).
- Instrument cluster.
Your best bet , take it to a qualified repair shop . You have no idea of the electronic's involved here .
PINPOINT TEST E: INCORRECT TEMPERATURE GAUGE INDICATION
Result / Action to Take
E1 RETRIEVE THE RECORDED DTCS FROM BOTH CONTINUOUS AND ON-DEMAND INSTRUMENT CLUSTER SELF-TESTS
- Use the recorded instrument cluster DTCs from the continuous and on-demand self-tests.
- Are any instrument cluster DTCs recorded?
If instrument cluster DTC U1073 is retrieved, REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual to continue diagnosis.
For all other instrument cluster DTCs REFER to the Instrument Cluster Diagnostic Trouble Code (DTC) Index.
GO to E2 .
E2 CARRY OUT THE COOLANT TEMPERATURE GAUGE ACTIVE COMMAND USING THE DIAGNOSTIC TOOL
- Connect the diagnostic tool.
- Key in ON position.
- Enter the following diagnostic mode on the diagnostic tool: Instrument Cluster Active Command.
- Select the instrument cluster engine coolant active command.
- Trigger the engine coolant active command. Scroll in three increments 0%, 50% and 100%.
- Did the temperature gauge start at cold when at 0%, move to half at 50% and full hot at 100%?
REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual to continue diagnosis.
GO to E3 .
E3 CHECK FOR CORRECT INSTRUMENT CLUSTER OPERATION
- Disconnect all instrument cluster connectors.
- Check for:
- pushed-out pins
- Connect all instrument cluster connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
INSTALL a new instrument cluster. REFER to Instrument Cluster in this section. TEST the system for normal operation.
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.