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Chevy Matiz 800 P0404 and P0401 Error Codes: Diagnosis and Fixes

Model: Chevy Matiz 800 Fault Code: P0401 Posted: 2017-11-18 02:40

Hello everyone, I'm Emilio from Italy and I recently encountered a recurring issue with my Chevrolet Matiz 800. The check engine light turned on, and after taking the car to a mechanic, they diagnosed a P0400 error code. I replaced the EGR valve with a new one, which temporarily resolved the issue. However, about a week later, the check engine light reappeared, this time showing a P0404 code. The problem persists even after the replacement. I'm seeking advice on how to properly diagnose and fix these codes. Any insights or recommendations would be greatly appreciated.

Related fault codes
P0401P0404
Comments (7)
Anonymous 2017-11-18 02:50

Hello everyone, I'm Emilio from Italy and I have a Chevrolet Matiz 800 with recurring check engine light issues. The mechanic initially found code P0400; after replacing the EGR valve, the code cleared. However, one week later, the light reappeared with code P0404. I'm looking for help to understand what might be causing this issue and how to resolve it.

Anonymous 2017-11-19 09:43

The EGR valve requires learning by the Powertrain Control Module (PCM). Try disconnecting the negative battery terminal for 10 seconds, then reconnect it. This can help reset the system and allow the PCM to relearn the EGR position.

Anonymous 2017-11-19 10:12

I tried disconnecting the negative battery terminal, but in some cases, the check engine light still comes back on after reconnection.

Anonymous 2017-11-19 12:39

After disconnecting and reconnecting the negative battery terminal, does the check engine light come back on with code P0404? Is this accurate? Do you have an OBD2 scan tool to view live data streams?

Anonymous 2017-11-19 12:54

Yes, after disconnecting and reconnecting the negative battery terminal, the check engine light turned on again with both P0404 and a new code—P0401—that was not present before. I use an OBD2 scan tool to read and clear these codes.

Anonymous 2017-11-20 05:04

Is this a linear EGR valve? The model year wasn't specified. If it's a linear EGR valve with a five-wire connector, the three inner wires are part of a 3-wire potentiometer sensor: 5V reference, signal (should read less than 100mV or ~0.1V), and ground. To test, use a multimeter with the negative lead connected to battery ground and probe each wire one at a time while the key is on and engine off. One wire should show 5V, one around 0.1V, and another approximately 0.75V.

Anonymous 2017-11-20 09:45

https://drive.google.com/file/d/1Ie7Q-q... (This is a three-year EGR valve replacement from 2006; I replaced it with a new one about a month ago. Now, the issue appears to be related to the pressure sensor. Does anyone think this might be the root cause? Thanks for your input.)