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Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 Engine Controls Power Relay Circuit Diagnosis

Circuit Description

The engine controls power relays coil and contacts are connected directly to the battery positive voltage (B+). The engine control module (ECM) controls the relay by grounding the control circuit through an internal solid state device called a driver. When the ECM detects a voltage on the ignition feed circuit, the ECM enables the engine controls power relay. The engine controls power relay controls the switched B+ circuit to the fuel pump relay coil, the fuel injectors, the heated oxygen sensor (HO2S) heaters and the other engine control components that use a switched B+ supply. The ECM also uses the switched B+ circuit to power up a portion of itself, including the circuitry which controls the malfunction indicator lamp (MIL) operation.

Diagnostic Aids

Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

Intermittent connections may cause the engine to stall or an intermittent loss of communication. Loss of the switched B+ voltage may cause multiple DTCs to set.

Test for poor connections at the ECM or at the component. Check all other circuits that are spliced to the engine controls power relay for the proper operation. Inspect the harness connectors for intermittent or poor connections. Refer to Testing for Intermittent Conditions and Poor Connections .

Refer to Symptoms - Engine Controls or Intermittent Conditions for the intermittents.

Test Description

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

  1. This step is to verify the remaining circuits required to operate the ECM and the engine controls power relay.

Step

Action

Values

Yes

No

Schematic Reference:

Power, Ground, VSS, and MIL


Object Number: 576159 Size: FS
Master Electrical Component List
Serial Data CAN Interface
Engine Controls Schematic Icons
Power Distribution Schematics
Theft Deterrent System Schematics
Power Distribution Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Turn OFF the ignition.
  2. Disconnect the engine controls power relay.
  3. Probe the battery feed circuits in the engine controls power relay harness connector with a test lamp connected to ground.

Does the test lamp illuminate on both circuits?

--

Go to Step 3

Go to Step 12

3
  1. Turn OFF the ignition.
  2. Disconnect the ECM C2 connector.
  3. Probe the engine controls power relay control circuit at the ECM connector with a test lamp connected to ground.
  4. Turn ON the ignition.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Probe the engine controls power relay control circuit at the ECM connector with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 5

5
  1. Reconnect the engine controls power relay.
  2. Probe the engine controls power relay control circuit at the ECM connector with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 8

6
  1. Set the DMM on the 10-amp scale in order to measure current flow.
  2. Connect the DMM between the power relay control circuit in the ECM harness connector and ground for 2 minutes.

Is the amperage within the specified range?

100-200 mA

Go to Step 7

Go to Step 14

7
  1. Disconnect the DMM from the engine controls power relay control circuit.
  2. Jumper the engine controls power relay control circuit to ground using a fused jumper wire.
  3. Probe the switched B+ supply circuits in the ECM harness connector with a test lamp connected to ground.

Does the test lamp illuminate on all three circuits?

--

Go to Step 15

Go to Step 9

8
  1. Test for an open or high resistance in the engine controls power relay control circuit.
  2. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 13

9
  1. Test for an open or high resistance in the switched B+ circuit from the relay to the ECM.
  2. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 13

10

Repair the short to voltage in the engine controls power relay control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

11

Repair the short to ground in the engine controls power relay control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

12

Repair the battery feed circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

13
  1. Inspect the relay connector for a poor connections or poor terminal tension.
  2. Repair as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 14

14

Replace the relay.

Did you complete the replacement?

--

Go to Step 18

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15

  1. Test the following circuits to the ECM for voltage:
    2. • Ignition positive voltage circuit
    • Battery positive voltage circuit
  2. Test the ECM ground circuit for the following conditions:
    3. • Loose connections
    • Corrosion
    • Open
    • High resistance
  3. Repair the circuits as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

16

Inspect the ECM harness connector for a poor connection or poor terminal tension. Refer to Testing for Intermittent Conditions and Poor Connections .

If a repair is necessary, refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 17

17

Important: 

   • Perform the idle learn procedure when replacing the ECM or the throttle body.
   • This vehicle is equipped with a theft deterrent system which interfaces with the ECM. Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle.

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the action?

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Go to Step 18

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18
  1. Connect a scan tool.
  2. Attempt to establish communication with the ECM.

Can communication be established with the ECM?

--

System OK

Go to Diagnostic System Check - Engine Controls