Left rear turn signal - 2010 Ford Escape Limited

Make sure that all the bulbs are the correct ones and have a good ground.

Turn Signal Lamps
The STOP/TURN/HAZARD fuse in the instrument panel (I/P) fuse block supplies battery positive voltage to the body control module (BCM) for the turn signal lamps. When the turn switch is placed in the LEFT TURN or RIGHT TURN position, ground is applied from G202 through the turn switch, to the turn signal switch signal circuit and to the BCM. The BCM then applies battery positive voltage to front and rear turn signal lamps supply voltage circuits. The left front turn signal lamp is grounded at G100, right front at G101, left rear at G301 and the right rear is at G302.

Turn Signal Reminder
The driver information center (DIC) activates the turn signal warning as requested by either turn signal switch. The turn signal warning sounds when the following occurs:
• The ignition is in RUN.
• The turn signal switch is in either turn position, sensing, within 1 second, an open to battery positive voltage transition in the turn signal control circuit, left or right turn.
• The vehicle has traveled a distance of 1.2 km (0.75 mi) by counting pulses in the rolling odometer class 2 message.
The DIC turns OFF the turn signal reminder when either the ignition switch is turned to the OFF position, or the turn signal switch returns to the OFF position, sensing within 1 second, no transitions from open to battery positive voltage in either of the turn signal control circuits, left turn or right turn.

My first step would be to hook up a factory scan tool an check for DTC'S - diagnostic trouble codes

DTC B3948 Left Front Turn Signal Circuit
Circuit Description
Ground is applied to the turn signal switch. When the turn signal switch is placed in the turn left position, ground is applied to the body control module (BCM) through the left turn signal switch circuit. The BCM then applies a pulsating voltage to the LF and LR turn signal lamps through the LF and LR turn signal voltage supply circuits.

What's the left rear lamp doing ? Flashing fast ?

DTC B3950 Left Rear Turn Signal Circuit

The flasher is under the dash.If you turn on the signal listen for it's location.Turn on your 4 way flasher and see if the left rear light is flashing.If it's not then replace the bulb.If it still does'nt work after replacing the bulb check if there is power to the socket. Use a probe light.If no power to the socket.There is a break in the wire or worse the signal switch may be the culprit

Has the vehicle been in an accident on the left rear side. First check the bulb to be sure it is not defective, trade it out with the side that works properly to test. If the bulb works well then My thought are you may have a shorted wire. The turn signal flasher works by heat build up within the flasher the heat is caused by the load of the bulbs, the load heats the metal spring causing it to open the circuit then as quickly as it cools down the circuit closes again lighting the bulbs.
There is also a possibility of a defect in the turn signal mechanism on the steering column. The turn signal switch on many models does three different things on many models that use the same bulb element / or bulb for brake and turn on rear of vehicle. It controls the circuit for brake light by sending power both left and right side rear when turn signal is in neutral position then when turn signal is in left turn the switch cancels brake light power to left side rear and supplies flasher power to left side while maintaining brake light supply to the right side rear, and so on opposite when the right turn is chosen on turn signal switch. The turn signal indicators on the dash normally run off the same circuit as front turn signal bulb only which is also controlled by turn signal switch. Front has turn signals but no brake light.
I think there is an additional load on the left side rear turn circuit and it could be either a wire that is shorted or the turn signal switch if the same bulb element is used for both functions.
Often times if trailer lighting is connected the flasher will also blink a little faster because of the extra load of additional bulbs.

Front right and rear right are on a different circuit than the left front an left rear. Locate the Flasher control module behind dash. With key in RUN position check for pulsing battery voltage on the Green/white wire coming out of the flasher control module electrical connector. If no battery voltage, check for battery voltage coming into the flasher from the turn signal switch on the white/red wire. Left turn input is on the white/black wire. If not battery voltage on white/red, but voltage on white/black when turning left, then the turn signal switch is bad

remove rear left lens and install new turn signal bulb.

Doesn't have a flasher , the BCM - body control module turns the turn signals on an off .
Turn Signal Lamps
The STOP/TURN fuse in the instrument panel (I/P) fuse block supplies battery positive voltage to the body control module (BCM) for the turn signal lamps. When the turn switch is placed in the left or right position, ground is applied to the BCM on the left or right turn signal switch signal circuit. The BCM then applies voltage to the appropriate front and rear supply voltage circuits.
Grounds for the various lamps are as follows:
• G100 supplies the right front lamps
• G101 supplies the left front lamps
• G400 supplies the right rear lamps
• G401 supplies the left rear lamps

See if bulbs have burnt out in the left brake light and rear turn signal (one bulb if combined) and also rear center high mount brake light.

If the left turn signal has a slower speed than the right turn signal, this is a symptom of a bulb or bulbs burnt out.

Usually, the wiring is not a problem, but I would not rule wiring (or sockets) as a problem out.

Good luck on this repair.

check the front right bulb