GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Engine Cooling Schematics

Connector End View Reference: Cooling System Connector End Views

DEFINITION: The after-boil coolant pump does not operate under certain conditions.

1

Did you perform the Engine Cooling Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Engine Cooling

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the Water Pump Control ON in climate control panel (CCP) special functions, miscellaneous test.

Does the after-boil coolant pump operate?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Disconnect the after-boil relay.
  2. Connect a test lamp between the control circuit of the after-boil relay and the coil supply voltage circuit of the after-boil relay.
  3. With a scan tool command the Water Pump Control ON and OFF.

Does the test lamp illuminate?

Go to Step 4

Go to Step 5

4

Connect a 5-amp fused jumper wire between the battery positive voltage circuit of the after-boil relay and the after-boil coolant pump supply voltage circuit of the after-boil relay.

Does the after-boil coolant pump operate?

Go to Step 12

Go to Step 8

5

Test the control circuit of the after-boil relay for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 6

6

Test the battery positive voltage circuit of the after-boil relay for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 7

7

Test the voltage supply circuit of the after-boil coolant pump 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 13

Go to Step 10

8

Test the voltage supply circuit of the after-boil coolant pump for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

9

Test the ground circuit of the after-boil coolant pump for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

10

Replace the HVAC Control Module. Refer to HVAC Control Module Replacement in HVAC Systems - Automatic.

Did you complete the replacement?

Go to Step 13

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11

Replace the after-boil coolant pump. Refer to Auxiliary Water Pump Replacement .

Did you complete the replacement?

Go to Step 13

--

12

Replace the after-boil relay.

Did you complete the replacement?

Go to Step 13

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13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2