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P0402 Excessive EGR Flow Diagnosis and Fix for 1996 Toyota 4Runner 2.7L 4-Cylinder

Model: 1996 Toyota 4Runner 2.7 4 Cyl Fault Code: P0402 Posted: 2009-08-19 17:17

Just had my 1996 Toyota 4Runner 2.7L 4-cylinder diagnosed at the dealership. They were professional and did not charge me to reset the P0402 code (Excessive EGR Flow). They mentioned that after resetting, the code should not return for approximately 200 miles of driving. I performed an EGR cleaning, which revealed only mild buildup — not severely clogged. The vehicle runs smoothly and has covered 136,000 miles with the check engine light on. Despite this, I'm seeking advice on how to properly diagnose and resolve the P0402 issue. Is there a specific component or system that should be inspected beyond EGR cleaning? Has anyone experienced success by replacing the EGR valve or checking vacuum switching components? PS: This forum is an invaluable resource — thanks for helping fellow owners troubleshoot common issues.

Related fault codes
P0402
Comments (5)
Anonymous 2010-04-06 13:58

I own a 2000 Toyota 4Runner 4-cylinder and am experiencing the same P0402 code. Unfortunately, I didn't have access to a good dealership — they reset the check engine light three times at my expense, and each time it returned. Last week, my belts started making loud squealing noises, so I replaced all three. However, the vibration associated with the P0402 code has returned. When I press the gas pedal, the car vibrates noticeably — it smooths out slightly above 50 mph and when I release the throttle. I'm completely frustrated by this recurring EGR issue and the cost of repeated repairs. It feels like a persistent design flaw.

Anonymous 2010-04-06 15:57

Have the mechanics checked the vacuum switching valve for the EGR system? What specific steps have they taken to address the problem, or are they simply clearing the code without performing any actual diagnostics?

Anonymous 2010-04-08 08:26

I posted this in August 2009 and still haven't resolved it — I'm glad to see renewed discussion. Jeff, could you clarify which switches should be inspected? I know a vacuum switch was replaced, but I wasn’t aware that any electronic or vacuum-controlled valves were involved.

Anonymous 2010-04-08 10:45

While I don't have the manual on hand, many vehicle brands — especially imports like Toyota — are known to suffer from EGR port blockages and uneven gas flow to cylinders. Could you please share a photo of your replaced EGR valve and describe any other work that has been done? That would help others understand potential root causes.

Anonymous 2013-02-04 18:56

I've now reached 150,000 miles and recently installed a brand-new EGR valve — the vibration improved temporarily, but the P0402 code reappeared. My next step is to plug and cover the EGR vacuum line to see if I can trigger a 'Low EGR Flow' code instead. I'll update this thread with results once I have them.