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.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 220 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L BI-FUEL)DIAGNOSTIC TESTSDTC P0300-P0304: ENGINE MISFIRE DETECTEDTEST DESCRIPTION
1999 GMC Forward Control 5.7 R, Automatic
Test Description
1999 GMC Forward Control 5.7 R, AutomaticSECTION Test Description
WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers in the diagnostic procedure.
- 4 - This step determines if the engine is misfiring while operating on the gasoline fuel system.
- 6 - The step determines if the condition exists. Remove the AF relay to ensure that the vehicle is operating on gasoline. Leave the relay out for the remainder of the diagnostic.
- 7 - This step verifies that the Crankshaft Variation Learn Procedure is performed. A crankshaft variation that is not learned may cause the misfire counters to increment.
- 9 - The spark should be consistent when you test the spark at the spark plug wires. The presence of few sparks then nothing indicates no spark.
- 12 - A misfiring cylinder may cause more than one misfire counter to increment. Diagnose the fuel injector circuit of the cylinder that displays the highest level of misfire.
- 17 - This step verifies that the catalytic convertor is operating correctly.
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.