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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Equinox 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC P1574

Circuit Description

This diagnostic test functions on the assumption that a sudden decrease in vehicle speed is caused by a brake pedal application. When the powertrain control module (PCM) detects that there is a 4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 seconds and a transition of the cruise/brake switch without a transition of the stop lamp switch, the PCM sets DTC P1574.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1574 Stoplamp Switch Circuit

Conditions for Running the DTC
    •  DTCs P0717, P0722, and P0161 are not set.
    • The engine speed is greater than 700 RPM.
    • The traction control system (TCS) or the antilock brake system (ABS) are not active and have not failed.
    • The vehicle speed is greater than 48 km/h (30 mph) in order to enable the diagnostic.
         The diagnostic will disable when the wheel speed is less than 16 km/h (10 mph).

Conditions for Setting the DTC
    • The vehicle speed decreases by at least 4.2 km/h (2.6 mph) within 0.25 seconds.
    • The PCM detects a torque converter clutch (TCC) brake switch/cruise release signal transition.
    • The PCM does not detect a stop lamp switch transition.

Action Taken When the DTC Sets
    • The cruise control system is disabled.
    • The PCM stores the DTC information into memory when the diagnostic runs and fails.
    • The PCM records the operating conditions at the time the diagnostic fails. The PCM displays this failure information in the Failure Records.
    • The malfunction indicator lamp (MIL) will not illuminate.

Conditions for Clearing the DTC
    • A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
    • use a scan tool in order to clear the DTC.

Diagnostic Aids

In order to avoid a misdiagnosis, perform the following:

    • Inspect for proper adjustment of the cruise release switch. Refer to Cruise Release Switch Adjustment .
    • Inspect for proper operation of the stop lamps. Refer to Exterior Lighting Systems Description and Operation in Lighting Systems.
    • Inspect for proper adjustment of the stop lamps. Refer to Stop Lamp Switch Adjustment in Lighting Systems.
    • For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number below refers to the step number on the diagnostic table.

  1. DTCs will set in the transmission control module (TCM) and the powertrain control module (PCM) when you perform this diagnostic table.

Step

Action

Yes

No

Schematic Reference : Cruise Control Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Press the brake pedal.
  4. With the scan tool, observe the Stop Lamp Pedal Switch parameter in the powertrain control module (PCM) Cruise Control data list.

Does the Stop Lamp Pedal Switch parameter display Released?

Go to Step 3

Go to Diagnostic Aids

3

Do the stop lamps operate properly?

Go to Step 5

Go to Stop Lamps Inoperative in Lighting Systems

4
  1. Turn OFF the ignition.
  2. Disconnect the throttle actuator control (TAC) module.
  3. Turn ON the ignition, with the ignition OFF.
  4. Connect a test lamp between the stop lamp switch signal circuit, at the female terminal side, and a good ground.

Does the teat lamp illuminate?

Go to Step 7

Go to Step 5

5

Test the stop lamp switch signal circuit for an open or for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 6

6

Inspect for poor connections at the harness connector of the PCM. 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 10

Go to Step 9

7

Inspect for poor connections at the harness connector of the TAC module. 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 10

Go to Step 8

8

Replace the TAC module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 10

--

9

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 10

--

10

  1. Use the scan tool in order to clear the DTCs in the PCM and the TCM.
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK