How do I find and change an 02 sensor on a 1991 Cadillac Deville 4.9 Liter engine

no engine told , or VIN , 4.5, 4.6 and 4.9 Liter???????
CALIF OR USA FED CAR, THEY ARE NOT THE SAME 1993 !


many cars have 2 cats for V6 and V8
and has Y pipe. and 3 sensors. 2front of cat, and 1 rear of cat
some cars have crossover manifolds, with just two, o2 sensors.
there service manual covers all this.

what I do is just look at both exhaust manifold exh headers
for 02 sensors.
looking at engine schematics the V8 has 2 sensors 02

the 4.9 LITER, IN CALIF HAS 4, THE FED MODELS HAVE 2.
SEE HOW TRICKY THIS, IS, ENGINE,CALIF/FED OR EXPORT CAR?
NORTHSTAR ENGINE HAS 2.

SORRY THERE IS NO ANSWER.
NO VIN TOLD
AND HOOD UP SEE EPA STICKER AND IF IT HAS WORD CALIFORNIA ON SAID STICKER IT IS .

WHAT i DO IS LOOK AT THE EXH.PIPES ALL. BINGO

I have a 2003 Deville...battery is under rear seat ...pull seat up and out to raise....battery itself is very easy to change out.
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1 8 4 3 6 5 7 2. Number 1 cylinder on the drivers side in the front of the engine. 2 is front passenger side.

This answer covers 1999-2005 Cadillac Deville, Eldorado & Seville.
Example Engine:
2002 Cadillac Seville STS 4.6L SFI DOHC HO 8cyl.

This engine has (2) Crankshaft Position (CKP) Sensors: the Upper sensor is CKP sensor B, and the lower sensor is CKP sensor A (this is included for the OBD-II DTC codes - P0385 references Sensor B = upper CKP sensor, whereas P0335 references the lower CKP sensor (sensor A)).

Both crankshaft position sensors are located in the front of the engine just above the oil filter adapter. To access both CKP sensors, jack up vehicle on the passenger side, remove the oil filter, and the oil filter adapter, including the Engine Oil Pressure (EOP) switch. See illustration.

The ARROW points toward Front of Car.
1. Upper Crankshaft Position Sensor (B).
2. Lower Crankshaft Position Sensor (A)
3. Engine Oil Pressure (EOP) switch
4. Engine Oil Level switch
The Oil Filter is the can-type object below the oil filter adapter, which includes the EOP switch. Recommend: remove oil filter with an oil filter socket/strap wrench, since it's close to the oil pan.

Sorry for the delay. Check this for 1991 Cadillac DeVille 4.9 liter V-8 VIN "B"




Hope helps (remember to rating this free answer).

your 8th digit of the serial number will tell you that. if it's 9 or Y = V8 4.6 liter, or if it's B = V8 4.9 liter

search ( mitchell1diy) this is a repair site you can access.

Check the fluid.Change the fluid and filter and see if it gets better.If it does then I would recommend a fluid transfer.This will transfer the old fluid and add new fluid.Hope this helps.Good luck.

I have a 1991 Cadillac Fleetwood 4.9 120000 miles, I have the same problem. replaced plugs,wires,cleaned throttle body, and O2 sensor and have same problem. Taking it to a GM shop on 02/24/10.

1989 1997 CADILLAC DEVILLE REPAIR MANUAL
You can simply get solution to your problem online here in this link