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P0430 and p0420 problems on 98 CSVT

Broken Bolts

CEG'er
Joined
Aug 30, 2010
Messages
49
Location
CT
Hello everyone. I have owned my 98 contour SVT for 7 months now and I absolutely love it! But every 400 miles I would get the check engine light to come on and when I scan it myself, it was p0430 catalyst efficiency below threshold bank 2. I would clear it and in exactly 400 miles, sometimes 350 miles, it would illuminate again and it was p0430. So I replaced the downstream (after the cat) oxygen sensor on bank 2, and I replaced the spark plugs (NGK iridiums), spark plug wires (bosch), and the fuel filter. Now 700 miles later the check engine light illuminates. I scan it and now it is p0420 cat efficiency bank 1. I'm thinking of replacing the downstream oxygen sensor on bank 1. Any ideas? I also would like to replace the upstream oxygen sensors as the engine has 130K miles on it at this point, but the upstream on bank 1 is impossible to get to. I can disconnect the wiring harness if I take the ignition coil pack off the engine but I still can't get a 22mm wrench or an oxygen sensor socket on the upstream oxygen sensor on bank 1. Has anyone replaced that sensor with the engine in place?
 
yes, there are various how-to's and notes on how to do it.

you can change the sensors, but unless you are getting codes for them you don't have to. The pre-cat codes are common and often false. you could just install some mil-eliminators.
 
Actually BrApple replacing the upstream sensors has been known to fix the P0420/0430 codes. reason being is the PCM looks at them as a reference for the lower sensors. if the upstream sensors are old they may have become a little lazy and dont switch as fast as they should (but not slow enough to throw a code for them). the slower switch rate of the lazy upstream sensors combined with the tight tolerances Ford programmed into the PCM (difference in switch rate between upstream and downstream is how CAT efficiency is determined) can cause the P0420/0430 codes to be thrown.
 
yes, if there was a O2 sensor code with the pre-cat codes. I have seen this before. everything I have ever come across is if the pre-cat codes are alone then they are "real" codes.

so at 130k the O2 sensors could be replaced, but they may not need to be.
 
(I just put this in the wrong post but here it is in the right one) I have had luck on two cars my 2000 svt and my wifes 99 mystique just replacing the upper O2s. This got rid of the codes and I think I have over 30 or 40k on the new sensors with no codes. I have never replaced the lower ones. My theory on why this is working is the computer is looking for the second O2s to lag behind the first O2s in a certain manner when you replace the upper ones the new ones respond much faster then the old ones causing the right difference. You could also do the MIL eliminator on the lower ones making the right difference in readings but maybe your uppers need replacing anyways. Same thing striker is saying. I did not have any O2 codes just the cat codes. This has proven to work on two of my cars for extended amount of time.
 
yes, if there was a O2 sensor code with the pre-cat codes. I have seen this before. everything I have ever come across is if the pre-cat codes are alone then they are "real" codes.

so at 130k the O2 sensors could be replaced, but they may not need to be.

I only had P0420 and P0430 with ~80K miles on the original upstream sensors. replaced both upstream O2s and never got the P0420/0430 codes again. I have done this, or seen this done, and it fixed the problem on numerous occasions, especially on cars that have old O2 sensors. over time the sensors just start to get a little slow at switching (lazy) but is still not slow enough to throw a code for slow switch rate. replacing the upstream sensors means you get the normal switch rate from them again and the P0420/0430 codes go away.
 
thats understandable. I got a pre-cat code on my 99 right before 80k also. but it was alone. I installed mil-eliminators and was good to go. One sensor had previously been replaced.
 
Thank you striker2 and svtavino for your replies. I finally got sick and tired of these codes coming on, so I started taking my car apart.

I replaced both of the upstream oxygen sensors on my SVT for bank 1 and 2. Yes, bank 1 sensor 1 was a •••••, but thanks to THIS SITE i was able to do it from the top. I still needed a flex head, extended bent handle 3/8" ratchet, a 3" extention and a deep oxygen sensor socket (with the slot cut on the side). Crows feet won't work, wrong angle.

I will post my results.
 
Wow, alot of good that did.

50 miles after replacing both upstream oxygen sensors, I get that ••••ing light on.

P0420
P0430 pending

ALLDATA says the ECT (Engine Coolant Temperature) sensor could be malfunctioning. I had problems with an ECT sensor and gauge sending unit on an 89 SHO I once had, they were all corroded from lack of coolant flushes and reading wrong. So I just replaced the ECT and the sending unit for the gauge (because my temp gauge always read low temperature).

While replacing the ECT, (which by the way is an even bigger ••••• to replace than bank 1 sensor 1 unless you have a SUPER DEEP 19mm 3/8" drive socket, cant use a wrench here unless you want to remove the starter) I noticed the upstream hose on the DPFE sensor (Differential Pressure Feedback EGR sensor) is split and leaking. That hose connects directly to bank 1 exhaust manifold before the catalytic converter. Did I just find the problem?
 
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not sure that you found the problem, because the wouldn't explain the code for the other bank, but its something that you should look into.

btw, where in CT are you?


also those codes are caused by what the downstream sensors are reading. have you gotten a scanner and watched the readings from the O2 sensors? You may need down stream sensors also, or it is what it is. The PCM will need to be reprogrammed or you need to just install mil eliminators.
 
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I have replaced the downstream oxygen sensors already. The car now has all 4 new oxygen sensors. It has a new ECT. All sensors that have to do with p0420 and p0430 have been replaced. If the codes come on again the cats are bad or like you said the PCM needs to be reprogrammed.
 
The ECT sensor is the reason for the P0420 and P0430 codes.

I tested my old one, and the signal return is correct for just the right amount of time to let the PCM enter closed loop. Then resistence raises, and it starts reading cold, causing the PCM to alter the air/fuel ratio causing it to dump fuel. But it never reads cold enough to re-enter open loop.

I had this same problem with an ECT sensor on an 89 SHO, only that car is OBD 1 and has no catalyst efficiency monitor.

It is definitly a Ford thing with the ECT's. Good ol FORD
 
10 months later, problem is still not fixed.

After replacing the ECT, the check engine light stays off for 2000 miles now instead of coming on every 400 miles. So changing the ECT did something, but did not resolve the issue. Replacing all 4 of the oxygen sensors did NOTHING but make the light come on every 50 miles. Took the precats off and they look brand new, what a waste of time and effort that was.

I've been searching the internet, racking the brains of ASE certified master technicians, using industry standard ALLDATA. NOBODY KNOWS HOW TO FIX P0420 and P0430.

All I keep hearing about when I read ALLDATA for hours, is misfire. Anything related to P0420 and P0430 is misfire, misfire this, misfire that. Thats all fine and dandy but I am not getting any misfire codes. Never got p0300 p0301 p0302 p0303 p0304 p0305 p0306, none never. But that doesn't mean the engine is firing 100%.

So I took the coil pack off and tested it, primary resistance across all pins .8 ohms perfectly in spec. Secondary resistance coil 1 = 13.01 thousand ohms, coil 2 = 13.18 thousand ohms, coil 3 = 13.28 thousand ohms. Spec is 12.8-13.1 thousand ohms. So 2 of my 3 coils have high resistance. Bought a new one and installed it 3 days ago.
 
I need a picture of a factory SVT intake air temperature sensor.

Mine is black with no o-ring and a flange like a coolant nipple to seal it.

The one they list for an SVT at autozone is white with an o-ring and no flange just a tab to twist and lock it.

The one they list for a 2.0 contour looks identical to the one installed on my SVT.

What is wrong here?

Do I have a 2.0 IAT sensor installed? Or is my sensor the factory part?

Chilton's manual shows 2.0 IAT to be a threaded metal sensor.
 
Some new new's about this problem, I have the P0420 code, I trying to resolve my problem, I think you need to replace the UIM / LIM Gasket , I will do this Satuday, and I be post my results, regards
 
Had this same problem. I replace all 4 O2s and still got this code on one bank. I ended up installing MIL eliminators. Problem solved!
 
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