P0420 - Cat Temp Gradient Normal - Alternator 14v? (1 Viewer)

[MH_Stevens]

After 223,793 miles I got my first "needs maintenance" light. Just the P0420 code "catalytic insufficiency bank 1".
First I measured the temperature increase across each cat and they were both 70 deg F, so I'm thinking not the catalytic converter. Next I tested the alternator output and at the battery posts it's only 14.0 volts. I'm sure last time I checked it was 14.5 volts. Wires to O2 sensors look sound. Gas cap was replaced a couple of years ago and "looks" OK. Not pressure tested.
Just had timing belt and water pump done and since then serpentine belt not perfectly aligned. It moves side to side with a slight sound on each pass."
Could that job have broken a vacuum hose?

Does this "say anything" to anyone?

Mike
PS My old 80 must go. Mechanics fine but interior a chicken coupe!

 

[looking4lc]

80% of the P0430 and 0420 codes caused of bad sensors. lots had success with replacing rear O2 sensors. Checking for a vacuum leaks and exhaust leak is a MUST before replacing anything. i recently had p0430 and (still observing) causes of dirty fuel filter.

 

[Joe422]

Yea, I have a re-occuring P0420 throughout the years, and replaced the O2 sensors (twice over a 260k mile period), and erase the codes. Still passes CA smog just fine.

 

[MH_Stevens]

My codes come right back.

 

[nukegoat]

I'd look at the sensor readouts/waveforms while running.

 

[2001LC]

If light on dash you're referring to, is "Maint". It nothing. That's reset every 5k to alert it's time to change oil.
Pull off drive belt and check those pulleys.


As the bearings go bad they sometime wobble a bit. Sometime pulley, put on backwards. Then they'll not seat properly.
If tension does not have sufficient spring tension, slippage can accrue. That and bad pulley bearings, can effect charge.

I was working on one today no CEL, with a P0430 pending.
History showed CEL with DTC of P0420 & P4030, coming and going for 9 moths.

Upon inspection, I found in this 03 w/155K:
LT FT running + 5.5% & 7%
Engine operating temp slightly low 181F to 184F on HWY.
Coolant 1 1/2 qts low.
Radiator fins, lower 1/3, clogged.
Air filter seal pinched, allowing air leak into air pipe. Air pipe was unusually dusty.
Found screw missing from fuel dampening device.
Dip stick with brunt appearance from tip to high mark.
All spark plugs factory originals, and walking out. #3, #5, #4 & #6 the loosest and #4 very very loose.
Coils & boost of loose plugs discolored and boots dry & cracking.
Compress low at #6 160PSI dry, 170PSI wet, 30% leak down. #2 175PSI, #4 178PSI # #* 187PSI
PS reservoir very dirty and smelly. Cap dip stick very black.
Brake res overfilled, dark and cap seal swollen.
Brake control wire corroded.
Fuel cap seal appeared okay, and hiss heard opening cap.

Proper PM is so important!

 

[MH_Stevens]

Great reply. Thanks. CEL is also ON

 

[MH_Stevens]

I'd look at the sensor readouts/waveforms while running.

What sensors, and how do I do that?

 

[nukegoat]

What sensors, and how do I do that?

O2 sensors. Buy a 12$ obd2 Bluetooth thing and download a free app on your smartphone

 

[MH_Stevens]

O2 sensors. Buy a 12$ obd2 Bluetooth thing and download a free app on your smartphone

Have OBD2 does not give any code for 02sensors. Just act bank1

 

[nukegoat]

Have OBD2 does not give any code for 02sensors. Just act bank1

Not codes, I mean - look at the real time data output from sensor 1 and sensor 2 of each bank

OXYGEN SENSORS: HOW TO DIAGNOSE & REPLACE

www.aa1car.com

Read that article

 

[MH_Stevens]

Sensor data good, in fact O2 voltages almost exactly the same both sides so having found cat and o2 seiners good started looking for air leaks and god and begorrah it was a good old cracked gas cap!!!!!!! Stole the gas cap of the 80 and alls well.

 

[MH_Stevens]

UPDATE I WAS WRONG ABOUT GAS CAP. Got new OEM gas cap and P042 code came back. I don't see any issues like 2001LC suggests. Live data for O2 sensors and CAT temp gain look good. Any other diagnostics to do? Shop did put in new spark plugs recently and fuel consumption became worse. Could wrong plugs or badly set plugs be issue?

 

[2001LC]

Could be bad set of plugs. Where they come from and what brand and type?

I've seen where MPG was very good, with very dirty air filter. Then change air filter with new, and MPG drop. Why! Well I suppose engine was being starved of air. ECM leans (reduces) the fuel by reducing fuel injector pulses to compensate. Same could be with spark plugs. They may have been beyond useful life and loose. Then engine would not have had good combustion. This dumps raw fuel into CATs. The ECM compensates by reducing fuel.

Did mechanic make any commits as to condition of old spark plugs?

 

[BullElk]

Not to hijack.... but I recently had the p0155 in one of my Hundys. I replaced two front sensors and so far has eliminated the code. However, now it has the p0420 code and never had it before. How might they be related?

 

[2001LC]

Not to hijack.... but I recently had the p0155 in one of my Hundys. I replaced two front sensors and so far has eliminated the code. However, now it has the p0420 code and never had it before. How might they be related?

Difficult to say. Faulty new sensor, air leak in exhaust, touched the prob, issue was not or not just O2 sensor to start with.