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P0300 and P1406 Error Codes on 1995 Chevrolet Blazer: Diagnosis and Fixes

Model: 95 Blazer Fault Code: P0300 Posted: 2006-10-17 19:46

I own a 1995 Chevrolet Blazer with two persistent error codes: P0300 (Random/Multiple Cylinder Misfire Detected) and P1406 (Manufacturer Control Auxiliary Emission Controls). The vehicle is difficult to start when cold—often requiring multiple attempts, turning the key off completely, and then restarting before it runs smoothly. It also feels sluggish during operation, which I suspect may be due to a misfiring cylinder. I've already replaced the spark plugs, ignition wires, distributor cap, and rotor, but both codes persist along with the starting issues. While I believe the catalytic converter is deteriorating, I'm confident this isn't the sole cause. The only other component I'm considering replacing is one or more fuel injectors—though at $300 each and a complex job, I'd like to verify it's truly necessary before proceeding. What troubleshooting steps should I take next? Are there any affordable or accessible diagnostics I can perform myself to identify the root cause?

Related fault codes

P0300P1406

Comments (7)

Anonymous 2006-10-18 08:25

Check fuel pressure, inspect for vacuum leaks, and ensure the EGR valve is functioning properly. These are common causes of misfires and emission control issues in older GM engines like the 1995 Blazer.

Anonymous 2006-10-18 11:11

Thanks for the reply! I'm wondering if taking my Blazer to a Chevrolet dealership for diagnostics would provide more accurate results than what Advance Auto Parts offered (at $85). Will their scan tool give me specific fault details, or do I need to systematically test components one by one? As a new user here, could you list the key checks beyond 'etc'? Also, since this car has been sitting unused for months, could gasoline condensate in the tank be affecting performance? I'm especially concerned about fuel injectors—my friend thinks it's them, but I'd like to verify before spending $300. This is a secondary vehicle used only for towing, so I want to avoid unnecessary expenses. Additional resources: motors, car, catalytic converter

Anonymous 2006-10-18 14:13

P1406 is a GM-specific code indicating an EGR valve issue. This could be directly linked to your P0300 misfire—either as a contributing factor or coincidental. It's worth investigating further, especially since EGR problems can cause poor cold starts and engine hesitation.

Anonymous 2006-10-19 07:19

While under the hood last night, I discovered that the ignition coolant temperature sensor has broken connectors. The wiring harness appears intact. Could this faulty sensor be contributing to the starting issues or misfire symptoms?

Anonymous 2006-10-19 07:42

You mentioned 'engine coolant sensor'—was that a typo? The correct term is likely ignition coolant temperature sensor.

Anonymous 2006-10-19 08:50

Here's the part link on Advance Auto Parts: http://www.partsamerica.com/ProductDetail...90&ptset=A. If you buy a Niehoff sensor, it’s an ignition coolant temperature sensor; if Borg Warner, it’s a regular coolant sensor. It threads into the engine block on the right side (facing the engine), about halfway down and halfway back.

Anonymous 2006-10-19 09:06

The dealership may not recognize 'ignition coolant temperature sensor'—they might refer to it as a 'coolant temp sensor.' I'd recommend replacing it first, especially since it's a common cause of starting issues and misfires. However, based on my experience, Niehoff sensors have often caused more problems than they solve—likely a typo on the website. Consider using a Borg Warner instead.