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.
2012 Chevrolet Sonic L4-1.8LFACTORY OEM SERVICE PROCEDURE
Compression Check: Testing and Inspection
Engine Compression Test
Removal Procedure
1. Remove the throttle body. Refer to Throttle Body Assembly Replacement Removal and Replacement.
2. Remove the spark plugs. Refer to Spark Plug Replacement Service and Repair.
3. Remove the relay holder cover.
4. Remove the fuel pump relay.
Measurement Procedure
Check Compression for all cylinders:
Note:
Engine revs at least 300/min.
1. Start the engine (approx. 4 seconds).
2. Compare the compression values.
Maximum pressure differential 100 kPa (14.5 psi)
Installation Procedure
1. Install the fuel pump relay.
* Place into the socket.
* Ensure the plug contacts are sound.
2. Install the relay carrier cover.
3. Install the spark plugs. Refer to Spark Plug Replacement Service and Repair.
4. Install the throttle body. Refer to Throttle Body Assembly Replacement Removal and Replacement.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.