The body control module (BCM) controls and monitors the state of the wiper control circuit. When the windshield wiper switch is placed in to a low speed setting, a signal is applied to the BCM. The BCM then applies battery positive voltage to the coil side of the WIPER relay through the WIPER relay control circuit. This energizes the WIPER relay, allowing battery positive voltage from the WIPER/WS fuse through the switched side of the WIPER relay to the windshield wiper motor. Ground is applied at all times to the coil side of the WIPER relay and the windshield wiper motor form G200.
This diagnostic procedure supports the following DTC:
DTC B3874 Wiper Low Speed Relay Circuit
• | The ignition is in the ON position. |
• | The ignition voltage is between 9-16 volts. |
The following conditions will cause the DTC to set:
• | The BCM detects an short to battery positive voltage in the WIPER relay control circuit for over 1 second. |
• | The BCM detects a short to ground or an open in the WIPER relay control circuit. |
The BCM will not activate the output.
• | The DTC will clear on current status after the condition for setting the fault is corrected. |
• | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
• | History and current DTCs can be cleared using a scan tool. |
Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections .
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Wiper/Washer Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Do the windshield wipers operate? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 |
Does the test lamp illuminate? | Go to Step 8 | Go to Step 4 |
4 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 6 |
5 |
Does the test lamp illuminate? | Go to Step 9 | Go to Step 7 |
6 | Test for a poor connection, an open, or short to ground in the WIPER relay control circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 10 |
7 | Test for a poor connection or an open in the ground circuit of the WIPER relay. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 11 |
8 | Repair a short to battery positive voltage in the WIPER relay control circuit. Refer to Circuit Testing and Wiring Repairs . Did you complete the repair? | Go to Step 12 | -- |
9 |
Does the DTC reset? | Go to Step 11 | Go to Step 12 |
10 | Replace the body control module (BCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 12 | -- |
11 | Replace the underhood electrical center. Refer to Underhood Electrical Center or Junction Block Replacement . Did you complete the replacement? | Go to Step 12 | -- |
12 |
Does the DTC reset? | Go to Step 2 | System OK |