DTC 025-026. Chevrolet Epica 2005

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 DTC 🢒 DTC 025-026

Circuit Description

The driver window switch signal circuits provide inputs to the intelligent switching unit (ISU) when the driver window switch is activated to the UP or DOWN position. These inputs allow the ISU to detect a window UP or DOWN request. The ISU provides power and ground to the driver window switche. When the driver window switch is activated to the manual UP or DOWN position, ground is supplied through the window switch to the signal circuit, which is pulled low. When the ISU detects low voltage on the signal circuit, it will command the window in the UP or DOWN direction. When the switch is released, the command ceases.

Conditions for Setting the DTC

•	The ISU detects a short to voltage on a window switch signal circuit.

•	Condition must be present for greater than 20 seconds.

Action Taken When the DTC Sets

Stores a current and history DTC 025 or 026 in ISU memory.

Conditions for Clearing the DTC

•	The ISU no longer detects a short to voltage on a window switch circuit.

•	A history DTC will clear after 40 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids

The following conditions may cause an intermittent malfunction:

•	There is an intermittent short to voltage in a window switch signal circuit.

•	A window switch is shorted to voltage internally or is sticking.

•	A window switch was pressed for longer than 20 seconds.

If the DTC does not reset after the code is cleared, then the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

Tests for the normal state of the window switch using a scan tool. The scan tool will display the normal state as Inactive, and Active when the switch is activated.

Tests if the ISU is able to detect a change in window switch state. The scan tool will display the normal state as Inactive, and Active when the switch is activated.

Tests for a stuck or shorted window switch. If the window switch is stuck or shorted, the state will change from Active to Inactive when the window switch is disconnected.

Tests for a short to ground in the window switch signal circuit.

Step	Action	Yes	No
Schematic Reference: Power Window Schematics Connector End View Reference: Power Door Systems Connector End Views
1	Did you perform the Door Systems Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Door Systems
2	Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, observe the appropriate window switch parameter in the ISU Miscellaneous Inputs data list. Does the scan tool display Inactive?	Go to Step 3	Go to Step 4
3	Activate the appropriate window switch. With a scan tool, observe the appropriate window motor parameter in the ISU Miscellaneous Inputs data list. Does the wiper washer switch parameter change state?	Go to Testing for Intermittent Conditions and Poor Connections	Go to Step 4
4	Turn OFF the ignition. Disconnect the driver window switch. Turn ON the ignition, with the engine OFF. With a scan tool, observe the window motor parameter. Does the scan tool display Inactive?	Go to Step 7	Go to Step 5
5	Test the signal circuit of the window switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 11	Go to Step 6
6	Inspect for poor connections at the harness connector of the intelligent switching unit (ISU). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 11	Go to Step 9
7	Test the signal circuit of the window switch for an open or short to voltage. Refer to hort to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 11	Go to Step 8
8	Inspect for poor connections at the harness connector of the window switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 11	Go to Step 10
9	Important: Perform the program procedure for the ISU. Replace the ISU. Refer to Intelligent Switching Unit Replacement in Body Control System. Did you complete the replacement?	Go to Step 11	--
10	Replace the driver window switch. Did you complete the replacement?	Go to Step 11	--
11	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?	Go to Step 2	System OK