: Oxygen Sensors......Need help soon!!!

04-01-04, 04:40 PM
Oxygen Sensors............Need help soon!!!!!!!!!!!! I have a 1997 Eldorado (ETC) which I recently had a blown head gasket fixed.
Time Certs and the works done.
I just had four oxygen sensors replaced yesterday, today the Service
Engine Soon light came on. I ran the dianostic and it gave me the same
four oxyen sensors I just replace a day ago.+ a MMM-B2150 CODE.
I called the machanic that installed the sensors and told him what happened and he seems to think that it is my Catalytic Convertor causing the
Any help will be appreciated!!!!!THANKS IN ADVANCE

P.S. Just want to say what a Great forum this is!!!!!!!!!!!!!!!!!

04-01-04, 05:08 PM
Had something similar happen to me with a past GM vehicle where a clogged fuel filter caused the O2 sensors to go bad along with the catalytic converter. The good new for me was the catalytic converter was covered under the factory warranty up to 80,000 miles instead of the standard.

04-01-04, 05:33 PM
Can you please post the out come of your problem.......I just replaced all four of the O2 sensors in my 96 STS and so far the light hasn't been back on but who knows it might come back on next week so I would really like to know the out come. You know three of the O2 sensors are very easy to change but the fourth one that's by the fire wall behind the coil was hell to change....I had to removed the coil and the blower motor just to have room to get to it (are you sure your mechanic changed that one?) did you see all four of the old ones? Keep me posted my friend and I hope everything works out for you as well.


04-01-04, 05:40 PM
I would expect O2 sensor problems to set a "P" code?.

Are your "new" O2 sensors GM parts?

Clear your code and wait for it to reset.

04-01-04, 05:43 PM
Agreed with Jim....

It could have been coincedence or somethign... WHat I owuld do is take it out for a few good WOT blasts and see if that doesnt help..... Things need cleaning and thats the easiest and most fun way to do it!

04-01-04, 07:32 PM
Yes, they are all GM Cadillac parts,, or that's what the mechanic told me.
The one's from the dianostic were "P0135, P0141, P0147 and P0155. Also
I got a MMM-B2150.

THANKS AGAIN GUYS!!!!!!!!!!!!!!!!

04-01-04, 09:16 PM
Yes, they are all GM Cadillac parts,, or that's what the mechanic told me.
The one's from the dianostic were "P0135, P0141, P0147 and P0155. Also
I got a MMM-B2150.

THANKS AGAIN GUYS!!!!!!!!!!!!!!!!

Check your fuses; all your "P" codes relate to "O2 sensor heater performance" problems. I have no idea where 'your' fuses might be located because my Service Manual is for a Seville. Under the hood is a good place to start. Look for a fuse that is labled something like "OXY SEN xx".

Your "B" code relates to the RF mirror circuit.

04-01-04, 11:58 PM
They are all O2 sensor heater codes. Seen aftermarket O2 sensors cause this. On OBDII systems you really need the GM parts. 4 GM O2 sensors can push $4-500 pretty easily....just for the parts.

Fuse could be blown on the heater circuit....maybe. Would have to look it up.


04-02-04, 01:19 AM
Fuses are good, sensors are GM....I just don't want to buy a new catalytic
converter to find out it's not the problem!!
Thanks again Guy's for all of your help!!!!!!!!!!!!!!!!

04-02-04, 08:52 AM
DO NOT replace your catalytic converter. If the converter was degraded you would have retrived DTCs P0420 / P0430. If your ho2s fuse is good like you say I would check your ho2s G-250 ground circuit, this ground circuit is related to all 4 sensors, I will be willing to bet it was left loose when the tech replaced your headgaskets. Lets us know what you find.
Frank T

04-02-04, 10:11 AM
I ordered all four of my O2 sensors from GM Parts Direct and they were like under $40 each (the dealer wanted $117 for each one) I also received them in five days from the day I ordered.


04-02-04, 11:06 AM
I think FrankT might be right. Looking at the codes/diagrams....all use ground circuit 250. The actual ground is G109. G109 is located 'left hand rear corner of the engine, near the park/netural switch.'

I dont think the cat is bad.

Also, it would be very easy to put aftermarket O2 sensors in and call them GM ones...


04-02-04, 05:51 PM
I took the Cad to Midas Muffler this morning and they said that the Catalytic
Converter had no cracks and was good. (This was before I read the recent
post on the forum). Anyhow, he asked if the machanic that put in the oxygen
sensors clear the codes with a scanner after he finished. I told him I thought
that he did, but wasn't sure. So cleared them (P0,,codes) with his scanner.
So for the "Service Engine Soon" light is out. I sure hope that it stay that
I sincerely thank all of you for the very helpful support that was given on
this forum and God Bless everyone of you!!
Thanks again,

04-03-04, 07:37 PM
Hi Guy's,

Today I drove the Cad about 26 miles and the "Service Engine Soon" light
has not come back on since the guy at Midas cleared all of the old codes
from the oxygen sensors. I hope that this is all that was wrong!!!!
Thanks again for all of your help, much appreciated!

04-04-04, 09:27 PM
Well the "Service Engine Soon" light came back on today after two days of
being off. Guess I will have to start all over again, no luck!!
Will keep everyone posted as to everything turn's out.


04-05-04, 02:13 PM
I would be willing to bet that forth sensor at the firewall wasn't changed......it is very hard to get to and removed.

04-05-04, 05:04 PM
The thing about it is that all four of the oxygen sensors show up on the
dianostics again!....seems maybe three would if just one was bad. But
all of the sames one that were replaced.
The Midas Muffler man suggested to go to a dianostic shop that would put
a sniffer in the tail pipe for testing. Sometimes they are able to find the problem.
I am to travel from California to Texas soon, is this serious enough to have
checked before traveling? Machanic says that eveything else seems ok.


04-05-04, 05:50 PM
I would just take it to the dealer and let them check it out and tell me what the problem is because they work on these cars all day long everyday...... then i would just take it some where else to have it repaired. Another thing i do from time to time is i go up to the dealer and catch one of their mechanic and just talk to him about the problem...i have done that more then once and they have been very helpful to me. I had the same problem you are having now myself and i change ALL FOUR of my sensors and my light hasn't been back on at all.

Good Luck:)

04-05-04, 07:42 PM
Hmmm....no bulletins. I guess the problem started with the head repair.

I think you will have to pull one of the O2 sensors and verify that it has 'AC Delco' printed in small letters around the base. I have personally seen aftermarket O2 sensors cause O2 heater codes on GM OBDII cars.

You could have 4 wrong GM O2 sensors (wrong part #.)

There are 2 fuses for the O2 heaters. Fuse #139, 10 amp 'oxy sen 1' , and fuse # 39, 10 amp 'oxy sen 2.' Both of these are locted in the engine comparment fuse/relay center. Its possible both fuses blew during the engine repair....or maybe the fuse link for the fuses burned up. Seen stranger things happen...so I guess it would be a good idea to verify 12 volts at the heater fuses in addition to checking the fuses.

All the sensors use the same ground. G109. Grounds are left off all the time during engine repairs. Or sometimes they are remounted in the wrong place....or are loose.


08-31-05, 06:33 PM
Another P0155 problem:
98 DeVille, replaced the front head gasket last spring, rear gasket tested ok.
fuel gauge giving wierd readings (related or not?) When full it shows empty. Dings for the first 5 gallons. Then everything is normal until 4 gallons left at which time it is empty. But I can live with that unless it is related to my other problems.
Current PCM P0132, P0155
History PCM P0151, P0154, P0300, P0463, P1381, P1527, P1599
History PZM B0533, B1771

The car is hard starting and the exhaust smells bad. Sometimes when idling the RPMs swing widely, like 200 rpm or more. Other times they are stable. It now dies on me from time to time. This seems to happen when approaching an intersection and I assume that the idle just swung too low and it quit.

When diagnosing the head gasket problem I broke one of a brand new set of spark plug wires and so replaced it with something from the salvage yard. Now thinking about buying a new set again anyway.

I am just at the stage of gathering information. Just purchased the 3 vol shop manuals for this car.

Called the Caddy dealer and the Olds dealer to price the O2 sensor and got different parts numbers. Would like to order from GMPartsDirect if I can find the right parts:
Bank 1 Sensor 1 -- part #25312203
Bank 2 Sensor 1 -- same part
GMPartsDirect also listed #25315373 (which one would be right?)
Olds dealer said: exhaust #25312211, engine out #25312197

Based on what I have been reading I am thinking of:
1. Check for disconnected ground wire G109 near the 'left hand rear corner of the engine, near the park/netural switch.' If the gound were left off wouldn't the other sensors show current errors?
2. Check for blown fuses in the fuse box (by the air intake?)
3. Replace the spark wires just so I know they are not contributing to the problem.
4. Replace the O2 sensors in the front and back exhaust manifolds.
(SevilleSTSJerome mentioned having to removed the coil and the blower motor just to have room to get to it. That sounds like going from the top of the engine. The manual talks about lowering the rear of the engine cradle 3 inches for this repair. Which is better?)

Thanks for any help you can give. I have learned a great deal from reading these forums.
Claude Richards