Uploaded August 2026 | Updated September 2026, 3 weeks ago

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In this video, we're taking a look at a Linear EGR system fault P0404 and P1404 on a 2002 GMC Yukon, and showing why understanding the circuit matters more than relying on a scan tool alone. When the bidirectional test keeps timing out, we switched to manual testing with a test light, jumper wire, and meter to identify the circuit design, verify EGR position feedback, prove the fault, and confirm proper flow. We also explain how to avoid damaging the PCM driver, why test lights still belong on computer-controlled circuits!!

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00:00 Introduction
00:45 Reading trouble codes
01:55 Checking EGR Scan Data
02:21 Bidirectional EGR Test
02:50 Fighting my scan tool
03:50 Testing the EGR Valve Manually
04:01 Power-Side vs Ground-Side Switching
05:28 Identifying the Circuit With a Test Light
06:10 Testing the EGR Position Sensor
07:03 Manually Powering the EGR Valve
08:28 Jumper Wire EGR Test
09:40 Testing EGR Flow With the Engine Running
10:33 Sticking EGR Valve Confirmed
10:51 Understanding Power-Side Switching
12:59 Removing and Cleaning the EGR Valve
16:32 Retesting With Bidirectional Controls
19:23 EGR Closed-Position Relearn
21:52 Do Test Lights Belong on Computer-Controlled Cars?
23:02 How the EGR Relearn Actually Works
25:02 Final Test Drive
29:00 Key Takeaways
31:43 Final Thoughts