Oxygen Sensor Replacement

I got codes 21 and 51 which indicate a faulty O2 sensor on my 91 Grand
Caravan with a 3.3Litre engine. What is the easiest way of changing the
Oxygen Sensor? The 3.3 Engine does not leave any room between the air intake
plenum and the firewall for access to anything on the righthand engine
cylinder head and the exhaust manifold. Do I need to remove the air intake
plenum to replace the O2 Sensor?

Thanks,

~Robert.

 

I have a 94 GC with 3.3 engine. Same body style IIRC. When my O2
sensor went, I watched the mechanic replace it.

He reached behind the engine between the engin and the firewall with a
pair of wire cutters. He cut the wires from the sensor, and removed
the connector & loose wires from the mating connector housing.

He then reached down to the sensor with a socket on the end of an
extension (can't remember if there was a universal on it or not), and
removed the old sensor.

The new sensor was installed, and torqued in place with a wrench, and
then the connector clipped into the system.

Elapsed time to re & re: 5 min. No hoist. Nothing weird. Took him
another 5 min to start the van and scope the sensor signal to make
sure it was responding properly.

hth

 

I cannot see any way as to how the mechanic could have been able to do that
with the air intake plenum on top almost touching the firewall. There is at
most 2 inches of space between the two, and there are vacuum fittings and
hoses in that area, but I will take a better look at the space between the
engine and the firewall.

~Robert.

 

I have a 94 T&C with the 3.8 and a 95 T&C with the 3.8 and I can't
see how you could torque it into place with a wrench from the top. I've
done my own O2 on the 95 and I came up from the bottom, it is easy
enough that way and plenty of clearance. I can see how you would
get it out with a socket and universal and extension - but only if it broke
free
right away, if it's like most O2 sensors an extension with a universal
would not apply enough torque. But there is not enough clearance from
the top to manipulate anything other than a stubby wrench and that would
not torque it down enough.

Ted

 

Here is what I did for my '96 T&C when the sensor needed replacement:

I went to a local garage and paid the guy $150 for the sensor and
replacement. Usually, this is the sort of thing I would do myself, but I
exercised the wisdom of understanding that it wasn't worth the effort this
time.

I'll make it up in something that I can do well. I didn't stick around to
see how it was done. Although after reading the previous account of the guy
who did it from the front of the engine, I am sorry that I did not.

Ken

 

That's a pretty easy repair, I think. I wouldn't go to a garage for it.

 

The physical install looked pretty easy; however, I do not have the
diagnostic equipment (simple though it is) to make sure that it was
indeed the O2 sensor that was faulty.

These days a shop bill of $150 is pretty low. Given the fact that I
was in and out of the shop in less than 30 min (a good 15 of which was
what it took them to write up the invoice and process the payment), I
would say that the conveinience factor was well worth paying the shop.

The only other side comment I have is that for the week following the
installation of the O2 sensor, my GC got well over 30 MPG in the city!
Then it returned to the "normal" 19 MPG.

 

An inexpensive, under $10, volt meter is all you need to test your O2 sensor.

 

The mechanic used a portable scope to diagnose mine. When he connected
it, you could see a solid 50% duty cycle square wave which did not
change with changing engine conditions.

Once the O2 sensor was replaced the O2 sensor output was a pure DC
voltage whice would hold steady for a given throttle position, but the
voltage output would change hen the trottle position changed.

I suppose you could use an analog volt meter to see if the voltage was
tracking properly, but a digital voltmeter would be a pain.

Pretty sure I've got an old analog voltmeter around somewhere. I'll
remember that next time! Thanks