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| P0141 and P0400; Update on codes | |
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| Tweet Topic Started: Feb 12 2010, 08:15 PM (2,651 Views) | |
| Dgeo | Feb 12 2010, 08:15 PM Post #1 |
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Advanced Member
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Just rebuilt my wifes car ('98 3/5) and been driving a week. Now I have both of these codes coming up. I cleaned the EGR valve when I rebuilt the engine. Is there something I missed that is now causing the P0400? The P0141 is the aft O2 sensor and I see the GPH increase on the scangage. Are these code related in any way? Would a bad cat cause P0141? Thanks for any input. |
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| Manny | Feb 12 2010, 08:27 PM Post #2 |
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Yes! a Costa Rican member
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Same issue happening to me, exactly the same codes and have not found the way to solve it |
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| mwebb | Feb 12 2010, 10:01 PM Post #3 |
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FOG
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there are good tutorials in the how to section about cleaning out the EGR passages ... the 02 sensor must cycle from 150 to 850mv and back in 100ms or less at 2k rpm hot does it ? get out your DVOM .... verify that the heater to the 02 sensor is powered up as well .. see the how to section about connecting with a T pin to connect . post test results and question for guidance . is it a front 0r rear 02 sensor DTC ? a bad front 02 sensor DTC will not be resolved by replacing the CAT - BUT the CAT might be killed by a bad front 02 sensor AND the TID 01 cat converter TESTs are suspended by the 02 sensor DTC , when you repair / replace the front 02 sensor the TID 01 cat converter testing will be enabled and the test will run it may not pass if the test fails , you will have a p0420 for cat efficiency |
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| Bad Bent | Feb 12 2010, 11:04 PM Post #4 |
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Facetious Educated Donkey
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I'll recommend checking out obd-codes.com/p0400 and obd-codes.com/p0401 Edited by Bad Bent, Feb 12 2010, 11:07 PM.
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| Woodie | Feb 13 2010, 11:44 AM Post #5 |
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0141 is the HEATER in the rear O2 sensor. Nothing to do with the cat, or the sensor itself, or engine performance. The computer is sensing a problem with something that the Federal government made them add in there for emissions reasons. Most likely the heater element built into the sensor has burned out, but it might be bad connections. 0400 is EGR, the problem is rarely the EGR valve or any of its control system, it is usually clogged passages leading to and away from the valve itself. Reach in there and physically move the EGR diaphragm with the engine running. It should stall out, or very close to it. With the engine running and the EGR valve off, you should have exhaust coming out of one hole and a lot of vacuum at the other. |
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| mwebb | Feb 13 2010, 12:21 PM Post #6 |
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FOG
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the two white wires on the rear 02 sensor are the heater connect with T pins as per the how to section , measure with the DVOM should be 14v across the heater pins with engine at hot idle AFTER the car has been driven over 50 mph .the rear 02 sensor heater does not get powered up until after the car has crossed the 50 mph threshold if there is 14 volts across the heater wires , the rear 02 sensor heater is fraked , and the rear 02 sensor will need to be replaced. if all is working as designed rear 02 sensor signal voltage (black wire) will be around 600mv or .6 volts at cruise voltage may cycle lazily from 150mv to 850mv and back until the cat converter lights off or if the cat is bad search in generic PIDs ; your scan gauge will show rear 02 sensor voltage at 1.27 volts until after the car crosses the 50 mph threshold and the heater gets powered up , if after crossing the 50 mph rear 02 sensor signal voltage is still at 1.27 volts , you will need to connect the DVOM to confirm presence of voltage at the heater . if there is no voltage present post test results for more guidance a bad rear 02 sensor DTC will not be resolved by replacing the CAT - BUT the TID 01 cat converter TESTs are suspended by the 02 sensor DTC , when you repair / replace the rear 02 sensor the TID 01 cat converter testing will be enabled and the test will run it may not pass if the test fails , you will have a p0420 for cat efficiency ================================================= see "GM Mode 6" in google find you car and system , study and learn Edited by mwebb, Feb 13 2010, 12:24 PM.
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| Dgeo | Feb 22 2010, 09:31 AM Post #7 |
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Advanced Member
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I replaced the rear O2 sensor this weekend and have driven the car for two days. The P0141 has stayed off, but the P0400 has come back on. The gas mileage is still way down also. I thought fixing P0141 would fix that, but it hasn't. Can the P0400 cause the rich condition? Now I have checked the EGR valve again, taking it off....cleaning it......making sure it moves, everything is fine there. I can rev the engine and see the valve diaphragm move, so the EGR valve should be good. Is it possible the modulator between the two EGR solenoids is bad, has anyone had this go bad? When I first removed the EGR to clean it, the nipple to the hose connecting to the bottom of modulator was clogged. Could this have damaged the modulator with the nipple being clogged? I checked the P and Q locations; can this be tested some how? What would be causing the awful gas mileage? Any help is appreciated. |
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| mwebb | Feb 22 2010, 11:15 AM Post #8 |
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FOG
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if you can see the EGR valve open off idle at around 2k rpm the modulator is functioning if you remove the EGR valve and start the engine there should be exhaust popping on the hole closer to the engine and intake vacuum sucking through the hole closer to the firewall JM put up a photo in another EGR thread thread . that would be the easiest way to figure out which which EGR passage is restricted ===================== the rear 02 sensor has no fuel trim authority and it should not affect fuel economy the EGR system will enhance fuel economy once it is functioning as designed |
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| Johnny Mullet | Feb 22 2010, 12:16 PM Post #9 |
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Fear the Mullet
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EGR system.............. http://geometroforum.com/topic/678529/ |
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