O2 Sensor codes . . .

[tpenfield]

I've been getting some O2 sensor faults on my port engine, and it looks like I don't have the proper 'Mercruiser PCM 112' manual to get more information & trouble shooting. The engine manual does not list the codes and refers to the PCM manual

From my Diacom Software, I am getting:
****************************************************
Fault Code: 871
Fault Type: 24
Code Desc: O2 sensor starboard S2
Type Desc: Input from sensor is above valid limit

Fault Code: 872
Fault Type: 16
Code Desc: O2 sensor heater starboard S2
Type Desc: ECU problem outputting signal to device
****************************************************
Engine is Mercury 6.2L DTS EC S/N 2A458510

I cleared them a couple of weeks ago, but they have come back.

I would like to get a better understanding of the codes before I load up the 'parts cannon'.

@muc ? @Fun Times ? Others ?

T.I.A.

 

[muc]

check for 12v on orange/black wire at position D at sensor
then check for ground at the other orange/black wire at position C
do these checks with engine running soon after starting.

This is what the manual recommends.
Unplug and replug the sensor, check the fuse, swap sensors. Note; must use another post cat sensor -- pre and post are different.

Fault Code: 871 -- O2 sensor starboard S2 (postcatalyst)
Fault Type: 24 -- Input high
Check the PCM‑to‑sensor circuit. To diagnose, replace
the suspect sensor with a known good sensor, or switch
the port and starboard sensors to determine if the fault
follows the sensor.

Fault Code: 872 -- O2 sensor heater starboard S2 (postcatalyst)
Fault Type: 16 -- Output fault Check the fuse and PCM‑to‑heater circuit. To diagnose, replace the suspect sensor with a known good sensor,
or switch the port and starboard sensors to determine if
the fault follows the sensor.

You should get a copy of the manual #8M0109714
Lots of good info!

 

[tpenfield]

Thanks @muc . . . Looks like I got to get one of those O2 sensor sockets to do the swapping.

In my engine voltage efforts, I did have an issue or 2 where one of the 10amp fuses got knocked loose. I'll have to check those again.

 

[alldodge]

Thanks @muc . . . Looks like I got to get one of those O2 sensor sockets to do the swapping.

Or if ya got a band saw you could make one, but being under $15 easy enough to buy

 

[Scott Danforth]

7/8" box wrench or deep well socket and a cut-off wheel if you don't have a band saw

 

[Fun Times]

Sorry Ted, but seems about the only thing I can suggest here is go buy a book (another service manual in your case) and join your admiral in the sun.



Some general info regarding the health of the catalyst exhadust,

http://download.brunswick-marine.com/filereader/file/pdf/5/enen/mercruiser/gasoline/8m0081787/8m0081787_7a.pdf

 

[tpenfield]

Thanks everyone for the help on this. Looks like I'll be buying the special socket and swapping left & right to see if the problem moves with the sensor.

 

[Lpgc]

I've been getting some O2 sensor faults on my port engine, and it looks like I don't have the proper 'Mercruiser PCM 112' manual to get more information & trouble shooting. The engine manual does not list the codes and refers to the PCM manual

From my Diacom Software, I am getting:
****************************************************
Fault Code: 871
Fault Type: 24
Code Desc: O2 sensor starboard S2
Type Desc: Input from sensor is above valid limit

Fault Code: 872
Fault Type: 16
Code Desc: O2 sensor heater starboard S2
Type Desc: ECU problem outputting signal to device
****************************************************
Engine is Mercury 6.2L DTS EC S/N 2A458510

I cleared them a couple of weeks ago, but they have come back.

I would like to get a better understanding of the codes before I load up the 'parts cannon'.

@muc ? @Fun Times ? Others ?

T.I.A.

Those 2 error code descriptions combined often point to the probe's heater circuit being shorted to its signal output, a problem with the probe itself or its wiring, in which case changing the probe (or fixing the wiring issue) is the fix. Good idea to swap probe positions to see if the error codes follow the probe.