2004 tahoe rear wiper motor works when you push washer button, but not when you turn on switch

Sounds like you might have a bad multifunction switch. You can test the outputs of the switch to confirm.

Rear Wiper/Washer System Components
The rear wiper/washer system consists of the following components:
• Rear wiper/washer switch
• Window wiper module-rear
• Window washer pump-rear
• RR WIPER 15A fuse
• RR WPRB 25A fuse
Rear Wiper/Washer System Operation
The rear wiper module controls rear wiper motor operation. Battery voltage supplied to the module is used to operate the wiper motor in all modes and to return the rear wiper arm to the park position after the ignition is turned off. Accessory voltage supplied to the rear wiper/washer switch is used to supply the rear window wiper and washer switch signal circuits. In wiper switch positions 1 and 2 the wiper switch signal circuit voltage level to the wiper motor module determines the wiper motor delay interval. The rear window washer pump supply voltage circuit is used to provide the operating voltage for the rear washer pump for as long as the rear washer switch is pressed. The rear window washer switch signal circuit is used as a wash signal to the rear wiper motor module to operate the wipers during the rear wash operation.


Did you replace the rear wiper module ?

Sounds like a wiring problem:
1. One of the wires attached to a pin in the connector attached to the wiring at the motor (not on the motor) may be corroded or have come loose, making intermittent contact, or
2. One of the wires in the harness between the motor and the switch is crimped somewhere around the tailgate and is intermittently opening, or
3. A bad motor ground wire connection at the tailgate.

How To Install Replace Rear Window Wiper Motor 2000 06 Chevy Suburban Tahoe

Replace wiper switch.Here's the switch.

It could be the wire or possibly the module itself. Access the module, remove the connector, and check for power on the gray wire terminal when the key and switch is on. No power, repair the wire. If there is power, replace the wiper module.

the relay that runs the motor

what is P13K?

check the fuse first. dealer can hook up NGS Tester and get fault codes to see what is wrong.

Principles of Operation
NOTE: The generic electronic module (GEM) will not activate the rear wiper system if either the liftgate or the liftgate glass is ajar. If either the liftgate or the liftgate glass becomes ajar while the rear wiper is in operation, the GEM will park the rear wiper motor.
There are two distinct modes of wiper operation:

• Off Mode: In this mode, there is no rear wiper activity, and the wiper motor will be in the PARK position.
• Interval Mode: This mode is selected when the rear wiper switch is in either the Interval 1 or 2 position. When this mode is selected, the rear wiper motor is driven up onto the glass by activating the rear wiper UP relay. When the wiper motor HIGH/LOW/PARK position input reaches the high position, the UP relay is deactivated and the DOWN relay is activated to reverse the wiper motor direction. When the wiper motor reaches the LOW position, as determined by the HIGH/LOW/PARK position input, the GEM deactivates the DOWN relay and will begin a new wiper cycle 1 to 10 seconds later, depending on the interval position selected.

To engage the rear window washer, rotate the rear window washer selector downward to the WASH position. The rear window wiper will run as long as the WASH position is selected. When the rear window washer selector returns to the OFF, INT 1 or INT 2 position, the washer will stop immediately, but the rear window wiper will continue for two to three sweeps and then return to its previous mode of operation.
The low washer fluid indicator chime warns that the washer fluid level is low. The low washer fluid indicator chime is a single tone with a duration of one second. The chime will sound when the low washer fluid indicator is initially activated.
The low washer fluid indicator warns that the fluid level in the washer reservoir is low. The low washer fluid indicator will illuminate when the washer fluid level is low and the ignition switch is in the RUN position.
The low washer fluid indicator will deactivate when the washer fluid reservoir is filled and the ignition switch has been cycled from RUN to OFF, then to RUN.
Inspection and Verification

1. The wiper/washer system is a generic electronic module (GEM) controlled system; refer to Section 419-10 .

1. Verify the customer concern by operating the wiper/washer system.

1. Visually inspect for obvious signs of mechanical and electrical damage.

Visual Inspection Chart Mechanical Electrical

• Hoses to windshield washer pump
• Wiper linkage

• Fuses 6 (5A), 8 (5A), 15 (5A), and 20 (5A)
• Wiring harness
• Loose or corroded connector(s)
• Relays
• Motors
• Multifunction switch
• Washer fluid level switch

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• The wipers are inoperative — rear

• Fuses 6 (5A), 8 (5A), 15 (5A), and 20 (5A).
• Circuitry.
• GEM.
• Multifunction switch (wiper/washer switch).
• Rear wiper up relay.
• Rear wiper down relay.
• Rear wiper motor.

Check 12 V supply. turn rear wiper switch on and test wiring to the rear wiper motor. If no voltage check fuse. If voltage, replace wiper motor.

sounds like the ground on the rear wiper motor isn't making a good ground contact , check the wiring see if its connected properly.