Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2006COBALT SS, 4D SEDAN, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 621 (ENGINE CONTROLS AND FUEL - 2.2L (L61) - DTC P0420 TO DTC P2544)DTC P0685, P0689, OR P0690CIRCUIT/SYSTEM TESTING
2006 Chevrolet Cobalt SS, 4D Sedan, Standard
Circuit/System Testing
2006 Chevrolet Cobalt SS, 4D Sedan, StandardSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2007 Pontiac G5 Pursuit, 2007 Pontiac G5, and 2007 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
- With the ignition OFF, remove the powertrain relay from the underhood fuse block.
- With the ignition ON, measure for battery positive voltage, B+, between the relay coil voltage supply circuit and ground.
- If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay coil. All wire circuit resistance should measure less than 2 ohms.
- Measure for voltage between the relay coil control circuit and ground.
- If voltage is measured on the control circuit of the relay, test for a short to voltage.
- Connect a test lamp between the battery positive voltage supply circuit of the relay coil and the relay coil control circuit. Use a scan tool to command the powertrain relay ON and OFF. The test lamp should turn ON and OFF when toggling between the commanded states.
- If the test lamp stays ON all the time, test for a short to ground on the relay coil control circuit. If the circuit tests normal, replace the ECM.
- If the test lamp stays OFF all the time, test for an open or high resistance on the relay coil control circuit. All wire circuit resistance should measure less than 2 ohms. If the circuit tests normal, replace the ECM.
- Measure for B+ between the relay armature supply circuit, and ground.
- If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay armature. All wire circuit resistance should measure less than 2 ohms.
- With the ignition ON, test for voltage on each test point of the ETC fuse.
- If voltage is present, test the ignition 1 voltage circuit between the ECM, the powertrain relay, and the ETC fuse for a short to voltage.
- If both circuits test normal, replace the ECM.
- Connect a 20A fused jumper wire between the B+ terminal and the ignition 1 voltage terminal of the powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the ETC fuse.
- If the test lamp illuminates at both test points of the ETC fuse, repair the ignition 1 voltage circuit between the powertrain relay and the ECM for an open or high resistance. If the circuit tests normal, replace the ECM. All wire circuit resistance should measure less than 2 ohms.
- If the test lamp only illuminates at one test point of the ETC fuse, repair the short to ground in the ignition 1 voltage circuit between the fuse and the applicable component. Replace the fuse, as necessary.
- If the test lamp does not illuminate on either test point of the ETC fuse, repair the open or high resistance between the powertrain relay and the ETC fuse. All wire circuit resistance should measure 2 ohms or less.
- With a test lamp, test for voltage on both test points of the following fuses:
- ETC Fuse
- Emission 1 Fuse
- If the test lamp fails to illuminate on one test point of each fuse, repair the open or high resistance between the fuse and the powertrain relay. All wire circuit resistance should measure 2 ohms or less.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.