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Possibly bad ground connection - G100
In back of the right headlamp on the frame. Headlamps, turn signals, parking lamp for the right all ground at that point. Corrosion in the wire, broken park lamp wire.
Headlamps, turn signals, parking lamp all have their own ground wire that connects at that point.
Hooking up a professional grade scan tool an check for DTC'S - diagnostic trouble codes in the BCM - body control module may point in a diagnostic direction.
DTC B3949: Right Front Turn Signal
Right Front Park/Turn Signal Inoperative
Circuit/System Description
The Body Control Module (BCM) controls the turn signals based on an input from the turn signal switch, part of the multifunction turn signal lever. The BCM receives an input from one of two signal circuits to determine which turn signal function is requested. When the turn signal lever is placed in the LEFT position, the left turn signal switch signal circuit is grounded indicating that left turn signal operation is requested. When the turn signal lever is placed in the RIGHT position, the right turn signal switch signal circuit is grounded indicating that right turn signal operation is requested.
When a turn signal input is received from the turn signal switch, the BCM will activate the appropriate turn signals. The BCM pulses voltage to the applicable turn signals via the turn signal lamp supply voltage circuits, illuminating the required turn signal lamps.
B3949
A short to voltage, short to ground, or an open/high resistance is seen on the right front turn signal lamp supply voltage circuit.
You know how to test electrical circuits? Using voltage drop.
The turn signals are controlled by the BCM
Turn Signal Lamps
The body control module (BCM) is responsible for controlling the turn signals and hazard lamps. When the turn signal switch is placed in either the left turn or right turn position, the BCM receives a signal from the turn signal switch. The BCM then sends an on-off voltage signal to either the left or right turn signals and their instrument panel cluster (IPC) indicator. When the hazard switch is pressed, the BCM receives a signal from the hazard switch. The BCM then will send an on-off voltage signal to all the turn signal lamps. All the turn signal lamps will flash including both IPC turn signal indicators.
I would suspect a problem with the BCM or maybe corrosion in the under hood fuse box . Wires from the BCM to the front turn signals go through the underhood fuse box.
Your best bet ,take it to a qualified repair shop that has a diagnostic scan tool that can read BCM DTC'S - diagnostic trouble codes
DTC B3948 Left Front Turn Signal Circuit
The body control module (BCM) controls the left front turn signal, hazard lamp, and daytime running lamp (DRL). The BCM supplies voltage to control the lighting functions. The BCM monitors the left turn signal lamp supply voltage circuit for proper operation.
DTC B3949 Right Front Turn Signal Circuit
Service Information
2002 Buick Park Avenue ' Park Avenue (VIN C) Service Manual ' Body and Accessories ' Lighting Systems ' Description and Operation ' Document ID: 643323
Turn Signal/Cornering Lamps
The HZDT/SIG fuse in the fuse block - underhood - left supplies battery positive voltage to the turn signal/hazard flasher module and have ground at G202. The turn signal lamps may only be activated with the ignition switch in the ON or ACCY position. The T/SIG fuse in the fuse block - underhood - left supplies battery positive voltage to the turn signal switch. When the turn signal switch is placed in either the left or right position, current flow is from the turn signal switch assembly to the turn signal/hazard flasher module. The turn signal/hazard flasher module then sends an on-off voltage signal to either the left or right turn signals and their instrument cluster (IPC) indicator. When the hazard switch is pressed, all the turn signal lamps will flash including both IPC turn signal indicators. The left turn signals have ground at G106, G400 and at G402. The right turn signals have ground at G105 and G400. The turn signal switch supplies battery positive voltage to the cornering lamps, the left cornering lamp has ground at G105 and the right cornering lamp has ground at G106.
2002 Buick Park Avenue ' Park Avenue (VIN C) Service Manual ' Body and Accessories ' Lighting Systems ' Description and Operation ' Document ID: 643323
Here is what the service manual says. Looks like it is not a flasher relay but a function of the body control module.
TURN SIGNAL AND HAZARD WARNING LAMP SYSTEMSystem Description OUTLINE Turn signal lamp and the hazard warning lamp is controlled by combination switch reading function and the flasher control function of BCM.
TURN SIGNAL LAMP OPERATION - BCM detects the combination switch condition by the combination switch reading function. - BCM supplies voltage to the right (left) turn signal lamp circuit when the ignition switch is turned ON and the turn signal switch is in the right (left) position. BCM blinks the turn signal lamp.
HAZARD WARNING LAMP OPERATION BCM supplies voltage to both turn signal lamp circuit when the hazard switch is turned ON. BCM blinks the hazard warning lamp.
TURN SIGNAL INDICATOR LAMP AND TURN SIGNAL SOUND OPERATION - BCM transmits the turn indicator signal to the combination meter with CAN communication while the turn signal lamp and the hazard warning lamp are operating. - Combination meter outputs the turn signal sound with the integrated buzzer while blinking the turn signal indicator lamp according to the turn indicator signal.
HIGH FLASHER OPERATION (FAIL-SAFE) - BCM detects the turn signal lamp circuit status by the terminal current value. - BCM increases the turn signal lamp blinking speed if the bulb or harness open is detected with the turn signal lamp operating. NOTE: The blinking speed is normal while operating the hazard warning lamp.
it's the grounds if they're both flashing fast it's definitely grounds take a test light and see if its got power goes through the test light grounded to the frame and if the light comes on then it's definitely your grounds
In my case the left front turn indicator lamp worked, but not the left rear indicator, although all the lamps would turn on with running lights activated, as well as the backup light and 'night-light' mode. The left rear turn indicator would not work with the hazard lights activated. I tested the combination switch (this is the left/right turn indicator switch you use when driving to indicate which direction you are going and is mounted/located on the steering column) and it tested O.K.. I had good continuity from the combination switch black wire, and resistance on the blue-white wire from there to the left rear turn indicator lamp, as well as good continuity on all wires going out from the left parking light fuse. Since the Haynes manual indicated that the flasher module was probably good if it made the tell-tale clicking sound, I was feeling perplexed. So I took it into a local shop that specialized in auto electrics and it turned out to be the flasher module. I was under the impression that it operated in a straight-forward left-right manner, but apparently it has a different circuit for each turn indicator lamp. So even if it is making the appropriate clicking sound when the combo switch is flipped, it could still be the flasher module. Obviously the manual leaves a bit to be desired in the troubleshooting of malfunctioning turn indicators.
I Think your turn signal switch is most probably faulty. So that, you will need to replace it. Please, check the video below. It shows the operations to replace the turn signal switch. I think that the operations are quite similar in most modern cars. Good luck!
How to Easily Replace a Turn Signal Switch - Clio 2 and other Renault/Dacia
If you have an aftermarket trailer plug on your truck, you are going to want to inspect the wiring to the plug, and the connections in the plug. I think it's shorting out.
If the right side signals are working properly and you can hear the signal flasher clicking when the right side signals are selected, the flasher is not the problem. Its more likely you have a short to ground in the left side wiring somewhere.
Service Information
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