Stop Lamps
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides a 5-volt reference voltage and low reference to the brake pedal position sensor. The position sensor provides an analog voltage signal back to the BCM that will increase as the brake pedal is applied. When the brake is applied, the BCM will then apply battery voltage to the left and right stop/turn signal lamp supply voltage circuits and the center high mounted stop lamp (CHMSL) supply voltage circuit illuminating the stop lamps. At the same time the BCM applies battery voltage through the signal circuit to the transmission control module (TCM) and the engine control module (ECM) indicating that the brakes are applied.
Ground for the stop lamps is supplied as follows:
• G402 provides ground for the left rear stop/tail/turn signal lamps
• G403 provides ground for the right rear stop/tail/turn signal lamps
• G301 provides ground for the CHMSL
The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.
Battery voltage from the LT TRN/SIG and RT TRN/SIG fuses located in the rear fuse block is also used by the body control module (BCM) for stop lamp operation.
Turn Signal Lamps
Battery voltage supplied to the body control module (BCM) from the fuses listed below is used for turn signal and hazard lamp operation.
• LT TRN/SIG fuse for the left turn signals
• CTSY/RF TRN fuse for the right front turn signal
• RR TRN/SIG fuse for the right rear turn signal
When the turn signal switch is place in either the LEFT or RIGHT position, ground from G300 is applied through the turn signal switch signal circuit to the BCM indicating the turn signal request. In response to this signal, the BCM applies a pulsating voltage to the front and rear turn signal lamps supply voltage circuits cycling the lamps ON and OFF. At the same time the BCM sends a GMLAN serial data message to the instrument panel cluster (IPC) to cycle the appropriate turn signal indicator ON and OFF.
Ground for the turn signal lamps is supplied as follows:
• G104 provides ground for the left and right front turn signal lamps
• G402 provides ground for the left rear stop/tail/turn signal lamps
• G403 provides ground for the right rear stop/tail/turn signal lamps
Do you have a factory scan tool (tech2) ? Your best bet , take it to the dealer .
SOURCE: 1991 volvo tail lights
Could you take out a bulb and with a testlight/probe check that you do in fact have power to that circuit .Also check that they are the correct bulb for that application I have seen people put indicator bulbs in where therse supposed to be a double filament bulb.Does the base of the bulbs lead contacts line up with the two steel terminals inside the plug?
SOURCE: brake lights/rear turn signals
I had the same problem with my 1999 Yukon. The electric board needed to be replaced. Rust starts to build up and shorts out or blows the bulb. The dealership charged $73.60 for the part and I installed it myself (Saved $30).
SOURCE: Brake lights dont work, Turn Signals all goofy
First thing i would do is chg. the break light switch, and make sure to chk. all grounds around tailights, sometimes if there is a ground problem it will travel back thru the hot wire to get a ground, witch in turn makes everything go wackey.
SOURCE: rear tail lights not working
If both tail lights are not working it is likely to be a fuse or bad connection under the hood or a connector at the back see if you can trace the wires to a connector and see if it is dirlty or corroded.
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