The front turn signals on my Grand Prix 2004 have stooped working. When I activate my turn signal for either direction the rear turn signals blink at double speed. I have replaced both bulbs in th

You have a body control module problem, more then likely . The BCM turns the turn signal on an off. Have a scan tool hooked up (a profesional grade scan tool ) One that can read codes in the BCM.

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.


DTC B3948 Left Front Turn Signal Circuit

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

Check the ground wires and also check that someone didnt put in a single element bulb where a double should be . Chuck

Hey I literally just today had the same problem, put a new bulb in the light was on but did not blink!!!! SUPER EASY SOLUTION, you simply have the bulb in too far. I gently pulled mine out a tiny bit and it started working fine... guarantee that's all that's happening to you!!!

you would need to buy a blinker relay

Check all the bulbs in the faulty side (front and rear), one of them must be the wrong type for application. Different blinking speed is the way of the system to tell you that something is not right. It only stops blinking if the bulb is burned out. I have seen that the most common problem is in the rear lights, using a stop light bulb ( two contacts) in the turn signal socket.

do you mean they dont blink? only on left side, but do blink on the right? put the hazrd flashers on and see if all works., if OK , then may be the turn signal switch of only the left side does not blink???

YOU HAVE TO REPLACE THE TURN SIGNAL SWITCH.BECAUSE WHEN IT GOES OUT.SOME TIMES YOUR DIMMER SWITCH STOP WORKING.IF YOU GOING TO FIX IT YOUR SELF BESURE TO.DISARM AIR BAGS FIRST.

likely not, but change /check anyhow....If problem persists, likely you will need to change the module that controls directionals (usually under dash to the right of steering column)