Principles of Operation

PRINCIPLES OF OPERATION

The instrument cluster and the smart junction box (SJB) use a combination of hardwired circuitry and the controller area network (CAN) to transmit and receive information. It is very important to understand:
- where the input (command) originates from.
- all the information (messages) necessary in order for a feature to operate.
- which module(s) receive(s) the input or command message.
- if the module which received the input controls the output of the feature, or if it sends a message over the CAN to another module.
- which module controls the output of the feature.

Each time the ignition switch is turned from OFF to ON, the charging system indicator, the low oil pressure indicator, and the malfunction indicator lamp (MIL) prove out and remain on until the engine is started. The safety belt indicator proves out for 60 seconds or until the safety belt is fastened. The air bag indicator proves out for approximately 6-8 seconds while the following instrument cluster indicators and warning indicators prove out for approximately 3 seconds:
- ABS warning indicator
- THEFT warning indicator
- brake warning indicator
- check fuel cap warning indicator (Escape, Mariner)
- 4x4 indicator (Escape, Mariner)
- low fuel level warning indicator (Escape, Mariner)
- Escape Hybrid hazard warning indicator
- service soon warning indicator
- overtemp warning indicator

Gauges

Speedometer (Escape, Mariner)
The instrument cluster receives the vehicle speed sensor (VSS) signal from the ABS module through the CAN circuits. The instrument cluster monitors the VSS input from the ABS module and commands the speedometer with a corresponding movement of the pointer.

Speedometer (Escape Hybrid)
The speedometer gauge feature informs the driver of the vehicle speed. The input to the instrument cluster is a CAN message from the transmission control module (TCM).

Odometer
The odometer and trip odometer are viewed through the message center in the integrated circuit display on message center clusters, or in the integrated circuit display on base clusters. The odometer is tamper-resistant and accumulates and registers up to one million miles in US mode or one million kilometers in metric mode, based upon rolling count data sent from the ABS module (Escape, Mariner) or the TCM (Escape Hybrid) via the CAN circuits. The trip odometer is resettable and accumulates and registers up to 999 miles or kilometers.

Fuel Gauge
The fuel gauge receives its signal from the fuel level sensor, a part of the fuel pump module. The fuel level sensor measures the variable resistance in the fuel tank depending on the current fuel level. When the fuel level is empty, the resistance in the unit is low (15 ohms ± 1 ohm). When the fuel level is full, the resistance is high (160 ohms ± 2 ohms).

Temperature Gauge (Escape, Mariner)
The powertrain control module (PCM) receives the engine coolant temperature status through hardwired circuitry to the engine coolant temperature (ECT) sensor and from the cylinder head temperature (CHT) sensor. The instrument cluster receives the engine coolant temperature data from the PCM through the CAN circuits. The instrument cluster monitors the engine coolant temperature data received from the PCM and commands the temperature gauge indication with a corresponding movement of the pointer. If the instrument cluster receives no signal the temperature gauge defaults to the cold position.

Tachometer (Escape, Mariner)
The tachometer is electrically operated and indicates the engine speed in revolutions per minute rpm). The tachometer range is 0 to 8,000 rpm. The tachometer receives the signal through the CAN circuits from the PCM. If the rpm information sent to the instrument cluster is invalid or missing, the instrument cluster defaults the tachometer to 0 rpm.

Tachometer (Escape Hybrid)
The tachometer gauge is to display the internal combustion engine revolution speed accurately and responsively and indicate when the vehicle is operating on electric power only (EV Mode). The tachometer range is 0 to 7,000 rpm. The tachometer receives the signal through the CAN circuits from the PCM. A small segment below 0 is used to indicate electric vehicle mode when the vehicle is using electric power only.

Charge/Assist Gauge (Escape Hybrid)
The charge/assist gauge feature is to let the driver know when the batteries in the electric drive portion of the vehicle powertrain are being charged by the internal combustion engine or regenerative braking system, or when energy from the batteries is being used to assist in moving the vehicle. The gauge movement is referenced from the battery and displays in units of kilowatts. Discharge (assist) is positive current and the gauge pointer rotates clockwise of the neutral position to a maximum of 40 kilowatts at 86 degrees. Charging is negative current and the gauge pointer rotates counterclockwise of the neutral position to a minimum of -40 kilowatts at 0 degrees. The input to the instrument cluster is over the CAN circuits from the traction battery control module (TBCM). The charge/assist gauge feature operates only when the ignition switch is in the RUN position.

Warning Indicator Lamps

Air Bag Warning Indicator
The instrument cluster is hardwired to the restraint control module (RCM). If an air bag system concern is detected, a diagnostic trouble code (DTC) is logged and the RCM provides a ground path to the instrument cluster illuminating the air bag indicator.

Anti-Lock Brake System (ABS) Warning Indicator
The ABS warning indicator is used to indicate an ABS concern or deactivation of the ABS. The instrument cluster, upon receipt of the ABS message from the ABS module through the CAN circuits, illuminates the ABS warning indicator.

BRAKE Warning Indicator
The parking brake switch is hardwired to the SJB and the brake fluid level switch is hardwired to the ABS module. The instrument cluster BRAKE warning indicator utilizes 2 inputs. The first input is provided by the parking brake switch and, when applied, provides a ground to the SJB which sends a signal over the CAN to illuminate the BRAKE warning indicator. The second input is controlled by the ABS module. The ABS module, upon receipt of a low brake fluid level signal or base brake system concern, provides a brake signal to the instrument cluster through the CAN. The instrument cluster, upon receipt of the brake signal, turns the BRAKE warning indicator on or off according to the monitored data.

Charging System Warning Indicator
The instrument cluster receives the charge signal from the PCM through the CAN circuits. When the generator (Escape, Mariner) or DC/DC converter (Escape Hybrid) output is insufficient to maintain the battery state of charge, the instrument cluster illuminates the charging system indicator.

Low Oil Warning Indicator (Escape, Mariner)
The instrument cluster is hardwired to the oil pressure switch. The oil pressure switch unit consists of a diaphragm and contact points, which are normally open. When there is low (under 41 kPa [6 psi]) or no oil pressure, the oil pressure switch remains open, removing the ground to the instrument cluster. When sufficient oil pressure exists, the oil pressure switch closes, providing a ground signal to the instrument cluster. The instrument cluster monitors the oil pressure ground signal and commands the low oil pressure warning indicator on or off according to the engine oil pressure.

Oil Pressure Indicator (Escape Hybrid)
The oil pressure indicator informs the driver that a low internal combustion engine oil pressure condition has been detected. The oil pressure switch is a normally-closed switch so that when there is no oil pressure the oil pressure switch is closed and the oil pressure input to the instrument cluster is grounded. The oil pressure is measured only when the internal combustion engine is running. The oil pressure indicator remains illuminated at the start of each ignition cycle until oil pressure is first sensed with the cycling on of the internal combustion engine.

Door Ajar Warning Indicator (Base Cluster)
The door ajar, the liftgate ajar, the liftglass ajar, and the hood ajar switches provide a ground signal to the SJB. The SJB, upon receipt of the door ajar ground data, supplies a door ajar status message to the instrument cluster through the CAN circuits. The instrument cluster monitors the door ajar status and turns the door ajar indicator (Escape, Mariner) or a display in the message center (Escape Hybrid) on or off according to the door ajar status message.

Safety Belt Warning Indicator
The RCM monitors the safety belt position through the safety belt switch (part of the buckle). When the safety belt is buckled, the RCM receives a ground signal and sends a message to the instrument cluster to turn off the safety belt warning indicator. When the safety belt is unbuckled, the ground to the RCM is removed and the RCM sends a message to the instrument cluster to illuminate the indicator. The passenger occupant classification sensor provides the status of the front passenger seat to the RCM through the high speed CAN circuits. The safety belt warning indicator may illuminate even though the driver side safety belt is buckled. This may occur if the passenger seat is occupied by an object with a significant amount of mass/weight which the occupant classification sensor classifies as an occupant. If the passenger safety belt is unbuckled, the safety belt warning indicator remains on even when the driver side safety belt is buckled. If the indicator is illuminated for this reason, this is a normal characteristic and no repair is needed.

THEFT Warning Indicator
The theft indicator alerts the operator that an anti-theft system malfunction has occurred or that the anti-theft system is armed when the ignition switch is in the OFF or ACC position. The theft warning indicator operates with CAN inputs from the PCM when the ignition switch is in the RUN and START positions and is controlled by the instrument cluster in the OFF and ACC positions.

Low Fuel Warning Indicator
The low fuel warning indicator is controlled by the instrument cluster and utilizes hardwired fuel level data from the fuel pump module. When the fuel level drops below a pre-determined level, the instrument cluster illuminates the low fuel warning indicator (Escape, Mariner) or a display in the message center (Escape Hybrid).

Indicator Lamps

CHECK FUEL CAP Indicator
The check fuel cap indicator is used to indicate significant leaks in the fuel tank evaporative system due to a loose fuel cap. The fuel tank pressure is monitored by the PCM and if a leak is detected it signals a fault to the instrument cluster over the CAN circuits. Once the PCM has detected a loose fuel cap and the indicator is illuminated, the indicator (Escape, Mariner) or a display in the message center (Escape Hybrid) remains illuminated until the fuel cap is secured and the ignition switch has been cycled one time.

High Beam Indicator
When the high beams are turned on, the SJB sends a signal to the instrument cluster through the CAN circuits to illuminate the high beam indicator.

O/D OFF Indicator (Escape, Mariner)
The instrument cluster receives the overdrive off signal from the PCM through the CAN circuits. The overdrive off switch is hardwired to the PCM. When overdrive is selected off, the overdrive off switch provides a ground signal to the PCM. The PCM, upon receipt of the overdrive off ground signal, provides a CAN overdrive off signal to the instrument cluster and the instrument cluster illuminates the O/D OFF indicator.

RH and LH Turn Indicators
The instrument cluster provides a ground for the RH and LH turn indicators. When the multifunction switch is in the RH or LH turn position, power is supplied to the instrument cluster from the SJB through hardwired circuitry and the RH or LH turn indicators flash on and off.

Malfunction Indicator Lamp (MIL)
The MIL is illuminated when a diagnostic trouble code (DTC) is detected by the PCM. The instrument cluster receives the MIL data from the PCM through the CAN circuits.

Speed Control Indicator
The instrument cluster receives the speed control signal from the speed control module through hardwired circuitry. When the speed control is engaged, the speed control module provides a ground to the instrument cluster to illuminate the speed control indicator (Escape, Mariner) or a display in the message center (Escape Hybrid).

4x4 Indicator
The instrument cluster receives the 4WD information from the 4WD control module through the CAN circuits. The module provides a 4WD status signal to the instrument cluster to illuminate the 4x4 indicator (Escape, Mariner) or a display in the message center (Escape Hybrid).

PRND21 Indicator (Automatic Transaxle Only) (Escape, Mariner)
The instrument cluster PRND21 indicator is a liquid crystal display (LCD) that displays the transmission range selected. Two sets of input signals are necessary for the PRND21 to operate correctly. The instrument cluster receives the transmission range signal through the CAN circuitry from the PCM and displays the appropriate range in the LCD. The brake shift interlock provides the second input signal. If the brake shift interlock input is not present, the P range is not highlighted in the LCD display.

PRNDL/Vehicle Odometer/Trip Odometer (Escape Hybrid)
The PRNDL indicates the transmission position selection on Escape Hybrid vehicles. This is done in the first line of the PRNDL/Vehicle Odometer/Trip Odometer LCD display. Each PRNDL character has a box surrounding it. The only time that the box segment is activated is when the requirements have been met to display the transmission position selected. The input to the instrument cluster is a hardwired input from the redundant park relay and a CAN message from the PCM.

Escape Hybrid Hazard Indicator
The Escape Hybrid hazard telltale informs the driver that the vehicle should be stopped or major damage to the propulsion system is probable. The input to the instrument cluster is through the CAN circuits from the PCM, the TBCM, and the TCM. The message STOP SAFELY NOW is displayed in the message center when this indicator is illuminated.

Overtemp Indicator
The overtemp indicator informs the driver of the following temperature related conditions in the vehicle. If the indicator is illuminated (not flashing), at least one of the following conditions exist:
- The internal combustion engine coolant is overheated.
- The electric motor coolant is overheated.
- The failsafe cooling feature is in Mode 1, which means the internal combustion engine is running a limited operating strategy in an attempt to reduce the engine temperature.

If the indicator is flashing, the failsafe cooling feature is in Mode 2, which means the internal combustion engine shuts down shortly due to an unresolvable engine over temperature condition. The input to the cluster is through the CAN circuits from the PCM.

Service Soon Warning Indicator
The service soon warning indicator informs the driver that vehicle service is required. The input to the instrument cluster is through the CAN circuits from the PCM, the TBCM, the TCM, and the power steering control module (PSCM).

Ready Light Indicator (Escape Hybrid)
The ready light indicator informs the driver that the electric drivetrain is ready to operate. This indicator is required because the internal combustion engine is not operating all the time and the driver needs to receive the information that the vehicle is on. The input to the instrument cluster is a CAN message from the PCM.