Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2005 Honda Element 2WD L4-2.4LFACTORY OEM SERVICE PROCEDURE
Engine Controls - MIL ON/DTC P0420 Stored
08-002
October 11, 2011
Applies To:
2005-06 Element - All Models With M/T
2005-06 Element: MIL Comes On With DTC P0420
(Supersedes 08-002, dated July 21, 2011, to revise the information marked by asterisks and black bars.)
REVISION SUMMARY
* Under WARRANTY CLAIM INFORMATION, the flat rate time was changed.*
SYMPTOM
The MIL is on, and DTC P0420 (catalyst system efficiency below threshold) is stored.
PROBABLE CAUSE
The ECM software misinterprets sensor inputs as a deteriorated catalytic converter.
CORRECTIVE ACTION
Update the ECM software, and check the three-way catalytic converter.
WARRANTY CLAIM INFORMATION
The normal warranty applies.
Failed Part: P/N 37820-PZD-A11
Defect Code: 03214
Symptom Code: 03203
Skill Level: Repair Technician
SOFTWARE VERSION
HDS Software Version: 2.012.013 (December 2007) or later.
Database Update: 27-Nov-2007 or later.
NOTE:
An incorrect HDS software version may indicate that the vehicle does not need an update.
The updated PGM-FI software program ID and P/N is shown. If this, or a later program ID, is the Current Program ID displayed during the update, the software for this service bulletin is already installed.
REPAIR PROCEDURE
1. Update the ECM with the HDS and software version 2.012.013 or later. Refer to Service Bulletin 01-023, Updating Control Units/Modules.
2. Clear the DIG with the HDS, and leave the HDS connected.
3. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) until the radiator fan comes on, then let it idle. Verify that the ECT sensor is above 158°F (70°C).
4. Test-drive the vehicle in 5th gear, between 45 and 75 mph, for at least 5 minutes, with the cruise control set, to warm up the three-way catalytic converter.
Then test the three-way catalytic converter by maintaining a vehicle speed of 25 mph or more, for at least 5 minutes, with the cruise control set.
NOTE:
The optimal speed to test the catalytic converter is 55 mph.
5. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS while driving.
Does the screen indicate PASSED?
Yes - The vehicle is OK at this time.
No - If the screen indicates EXECUTING, keep driving until a result appears. If the screen indicates OUT OF CONDITION, go to step 4. If the screen indicates FAILED, replace the three-way catalytic converter.
NOTE:
In most cases, DTC P0420 is caused by the ECM software. In rare cases, the three-way catalytic converter needs to be replaced.
Disclaimer
October 11, 2011
Applies To:
2005-06 Element - All Models With M/T
2005-06 Element: MIL Comes On With DTC P0420
(Supersedes 08-002, dated July 21, 2011, to revise the information marked by asterisks and black bars.)
REVISION SUMMARY
* Under WARRANTY CLAIM INFORMATION, the flat rate time was changed.*
SYMPTOM
The MIL is on, and DTC P0420 (catalyst system efficiency below threshold) is stored.
PROBABLE CAUSE
The ECM software misinterprets sensor inputs as a deteriorated catalytic converter.
CORRECTIVE ACTION
Update the ECM software, and check the three-way catalytic converter.
WARRANTY CLAIM INFORMATION
The normal warranty applies.
Failed Part: P/N 37820-PZD-A11
Defect Code: 03214
Symptom Code: 03203
Skill Level: Repair Technician
SOFTWARE VERSION
HDS Software Version: 2.012.013 (December 2007) or later.
Database Update: 27-Nov-2007 or later.
NOTE:
An incorrect HDS software version may indicate that the vehicle does not need an update.
The updated PGM-FI software program ID and P/N is shown. If this, or a later program ID, is the Current Program ID displayed during the update, the software for this service bulletin is already installed.
REPAIR PROCEDURE
1. Update the ECM with the HDS and software version 2.012.013 or later. Refer to Service Bulletin 01-023, Updating Control Units/Modules.
2. Clear the DIG with the HDS, and leave the HDS connected.
3. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) until the radiator fan comes on, then let it idle. Verify that the ECT sensor is above 158°F (70°C).
4. Test-drive the vehicle in 5th gear, between 45 and 75 mph, for at least 5 minutes, with the cruise control set, to warm up the three-way catalytic converter.
Then test the three-way catalytic converter by maintaining a vehicle speed of 25 mph or more, for at least 5 minutes, with the cruise control set.
NOTE:
The optimal speed to test the catalytic converter is 55 mph.
5. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS while driving.
Does the screen indicate PASSED?
Yes - The vehicle is OK at this time.
No - If the screen indicates EXECUTING, keep driving until a result appears. If the screen indicates OUT OF CONDITION, go to step 4. If the screen indicates FAILED, replace the three-way catalytic converter.
NOTE:
In most cases, DTC P0420 is caused by the ECM software. In rare cases, the three-way catalytic converter needs to be replaced.
Disclaimer
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.