# 1999 Honda Accord 4 P Codes Related 2 Dirty Air **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** accord\ **Created:** [December 6, 2017, 3:07pm UTC](https://community.cartalk.com/t/1999-honda-accord-4-p-codes-related-2-dirty-air/110058 "2017-12-06T15:07:21Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Goulash\_Innovation](https://avatars.discourse-cdn.com/v4/letter/g/3bc359/32.png) [@Goulash\_Innovation](https://community.cartalk.com/u/Goulash_Innovation)\ **Post date:** [December 6, 2017, 3:07pm UTC](https://community.cartalk.com/t/1999-honda-accord-4-p-codes-related-2-dirty-air/110058/1 "2017-12-06T15:07:21Z")
P0430/P0420/P0705/P0401 I failed an emissions test on “Exhaust Gas Recirculation Flow Insufficient Detected”. I am thinking after driving in a metropolitan environment with dirty dirty air that there are several parts that just need to be cleaned. ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [December 6, 2017, 11:07pm UTC](https://community.cartalk.com/t/1999-honda-accord-4-p-codes-related-2-dirty-air/110058/2 "2017-12-06T23:07:49Z")
I might guess all the codes are related to one problem, I am not a mechanic, but I would guess you need one. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [December 6, 2017, 11:23pm UTC](https://community.cartalk.com/t/1999-honda-accord-4-p-codes-related-2-dirty-air/110058/3 "2017-12-06T23:23:42Z")
> **[P0430 - OBD-II Trouble Code](https://repairpal.com/obd-ii-code-p0430)** > > Definition of error code P0430 - Catalyst System Efficiency Below Threshold (Bank 2). Read emissions expert information and diagnostics for fault code P0430 > **[P0420 - OBD-II Trouble Code](https://repairpal.com/obd-ii-code-p0420)** > > Definition of error code P0420 - Catalyst System Efficiency Below Threshold (Bank 1). Read emissions expert information and diagnostics for fault code P0420 > **[P0705 - OBD-II Trouble Code](https://repairpal.com/obd-ii-code-p0705)** > > Definition of error code P0705 - Transmission Range Sensor Circuit malfunction (PRNDL Input). Read emissions expert information and diagnostics for fault code p705 > **[P0401 - OBD-II Trouble Code](https://repairpal.com/obd-ii-code-p0401)** > > Definition of error code P0401 - Exhaust Gas Recirculation Flow Insufficient Detected. Read emissions expert information and diagnostics for fault code P0401 You’re going to need a mechanic. Tester ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [December 7, 2017, 3:17am UTC](https://community.cartalk.com/t/1999-honda-accord-4-p-codes-related-2-dirty-air/110058/4 "2017-12-07T03:17:58Z")
The codes are numbered the way they are to give you some idea which problem to address first. This minimizes interactions doing it in that order. And sometimes higher number codes will automatically be fixed when the lower number one is. So ask you shop to start by fixing the problem causing the lowest numbered code; i.e. p0401, the EGR problem. You might have a faulty egr valve, or the vacuum control which control how far it is supposed to open it is broken. If I had that problem on my Corolla first thing I’d do is verify the egr valve holds vacuum ok. EGR valves have a flexible rubber diaphragm in them which sometimes over time develops a leak. If it held vacuum, next thing I’d do is verify when full intake manifold is applied to it at warm idle, doing that stalls the engine. That will verify the EGR valve is capable of moving through its full range.