Expedition code 420


rayjag
06-04-2006, 09:12 PM
Has anyone had any experience with a ford (expedition)having a check engine light on with code 0420?

RJ

way2old
06-05-2006, 06:15 PM
P0420 is for bank 1 catalyst operating below efficiency. This is a common code for Fords we have in our fleet. The cause can be anything from high/low fuel pressures, ignition misfire, exhaust leak, vacuum leak, bad Maf reading, bad O2 sensor readings, bad O2's, or a bad converter. Usually there is a root cause for the catalyst codes. The test for tha codes are about 7 pages long. Good luck.

MT-2500
06-12-2006, 03:24 PM
Has anyone had any experience with a ford (expedition)having a check engine light on with code 0420?

RJ

As Way2old said there is many test to run for that code.
First things to check is the tune up end. Make sure engine running is up to par.
If under 80K and or under 8 years and cat is bad it is covered under federal emmisions waranty.

Here is a few guide line for testing.
Good luck MT

DTC P0420, P0421, P0430 & P0431: Check Possible Cause Of Misfire DTC P0420 and P0421 indicates bank one catalyst system efficiency is minimum requirement. DTC P0430 and P0430 indicates bank 2 catalyst system efficiency is minimum requirement. Possible causes are as follows: Use of leaded fuel. Oil contamination. Cylinder misfire. Fuel pressure too high. HO2S sensor improperly connected. Damaged exhaust system component. Faulty ECT sensor. Faulty HO2S. Ensure ignition timing is correct. Retrieve all Continuous Memory DTCs. If misfire code(s) is not present, go to next step. If misfire code(s) is present, isolate cylinder and repair as necessary. Check HO2S Monitor DTCs If DTCs P0136, P0138, P0140, P0141, P0156, P0158, P0160, or P0161 were present in step 1), service as necessary before continuing. If none of these codes are present in step 1), go to next step. Check ECT Sensor DTCs If DTCs P0117, P0118, P0125 or P1117 were present in step 1), service as necessary before continuing. If none of these codes are present in step 1), go to next step. If any codes except P0420, P0421, P0430 and/or P0430 were present in step 1), service as necessary before continuing. If no codes except P0420 and/or P0430 were present in step 1), go to next step. Check Rear HO2S Wiring Harness Turn ignition off. Ensure HO2S wiring harness is correctly routed and connectors are tight. Repair or replace as necessary. If wiring harness and connectors are okay, go to next step. Check Fuel Pressure Turn ignition off. Release fuel pressure. Install fuel pressure gauge. Start engine and allow to idle. Note fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain for one minute. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST HC . Check For Exhaust System Leaks If exhaust system leaks, it may cause catalyst monitor efficiency test to fail. Inspect exhaust system for cracks, loose connections or punctures. Repair or replace as necessary. If exhaust system is okay, go to next step. Check For Exhaust System Restrictions Inspect exhaust system for collapsed areas, dents or excessive bending. Repair or replace as necessary. If exhaust system is okay, go to next step. Check Manifold Vacuum Install tachometer. Connect vacuum gauge to intake manifold vacuum source. Start engine and raise engine speed to 2000 RPM. Manifold vacuum should rise to more than 16 in. Hg. If manifold vacuum is okay, go to next step. If manifold vacuum is low, go to step 11). Leave tachometer and vacuum gauge connected. Start engine and raise engine speed to 2000 RPM. On a non- restricted system, manifold vacuum should quickly rise to normal range as increased RPM is maintained. On a restricted system, manifold vacuum will slowly rise to normal range as increased RPM is maintained. If manifold vacuum is okay, no indication of exhaust leak or restriction has been detected and testing is complete. If manifold vacuum is low or slow to respond, go to next step. Leave tachometer and vacuum gauge connected. Remove exhaust pipe from exhaust manifold. Start engine and raise engine speed to 2000 RPM. If manifold vacuum is now okay, fault is downstream from exhaust manifold. Reconnect exhaust pipe to exhaust manifold and go to next step. If manifold vacuum is still low or slow to respond, fault is in exhaust manifold or intake manifold gasket. Repair or replace as necessary and repeat QUICK TEST. Leave tachometer and vacuum gauge connected. Disconnect muffler/tailpipe assembly from rear of catalytic converter. Start engine and raise engine speed to 2000 RPM. If manifold vacuum is now okay, fault is in muffler/tailpipe assembly. Repair or replace as necessary and test drive vehicle to verify elimination of symptom. If manifold vacuum is still not okay, fault is in catalytic converter. Repair or replace as necessary. Check tailpipe/muffler assembly for debris from catalytic converter. Test drive vehicle to verify elimination of symptom.

s.mac22
05-10-2010, 07:29 PM
I know this is an old post but a new problem for me. I got this code on my 01 Expo and after reading the troubleshooting post, I'm curious about the exhaust system leak causing the code to come up. I checked my exhaust system and found that the tailpipe is cracked (1/8in wide)at the bend right above the rear axle. I can post pics if needed. I havn't repaired it yet but the question is:
Would the crack behind the muffler still cause the system to depressurize?

If so, this may be the problem that is making the code come up....I hope!

MT-2500
05-11-2010, 08:07 AM
I know this is an old post but a new problem for me. I got this code on my 01 Expo and after reading the troubleshooting post, I'm curious about the exhaust system leak causing the code to come up. I checked my exhaust system and found that the tailpipe is cracked (1/8in wide)at the bend right above the rear axle. I can post pics if needed. I havn't repaired it yet but the question is:
Would the crack behind the muffler still cause the system to depressurize?

If so, this may be the problem that is making the code come up....I hope!

No way.

Best to start a New thread on your problem and give us all details and info on it and someone will help you.

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