02 Buick LeSabre Ltd. Rear flashers work (blinking rapidly), front bulbs stay on, inside indicators also flash rapidly. Replaced control module under the dash. Did not help. What else could it be?

Well Joey I have a factory diagnostic chart here in front of me , 16 steps ! Including the part you already replaced ,they mention shorts , instrument cluster , the turn signal/multifunction switch


step 2

Turn ON the ignition, with the engine OFF.
1. Observe the turn signal lamps and indicators.
2. Turn ON and OFF the right and left turn signal lamps.
3. Turn OFF the ignition.

Do the turn signal lamps and indicators operate properly?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Are only the turn signal indicators always ON or flashing?
Go to Step 6
Go to Step 4

4

Test the always ON or flashing turn signal bulb voltage supply circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 16
Go to Step 5

5

1. Disconnect the turn signal and hazard flasher module.
2. Connect a test lamp between the always ON or flashing turn signal input circuit of the turn signal/hazard flasher module and a good ground.
3. Turn OFF the always ON or flashing turn signal.

Does the test lamp illuminate?
Go to Step 7
Go to Step 8

6

1. Disconnect the Instrument panel cluster (IPC).
2. Connect a test lamp between the always ON or flashing turn signal indicator supply voltage circuit and the IPC ground circuit.
3. Turn OFF the always ON or flashing turn signal indicator.

Does the test lamp illuminate?
Go to Step 12
Go to Step 11

Hi there., when flashers/indicators work rapidly on the dashboard you should check whether it is the same on the actual bulds. Fadt flashing is usually a sign of a bulb failure somewhere. If everything is functioning ok externally I would consult a competent technician for a diagnosis.