Oxygen sensors Location

There are two located before the catalysts, and two located after the catalysts. I believe the wide band go before(pre-cat/bank 1-2 sensor 1), the others should be visible/accessible from below. Just out of curiosity, why are you replacing all four? The are not normally a maintenance item, and for all of them to be failed is rare.

The P1825 is for an invalid IMS which is in the transmission, what used to be known as the range switch. The P0700 is a code for the transmission control module requesting the check engine light to illuminate. The p0036 and 0056 are bank 2 oxygen sensor heater codes, this does not indicate that they are faulty, and the fact that there codes for both of them may indicate a fault in the circuit that powers both of them. Assuming of course that they had not been recently disconnected with the key turned on. I would check the POST O2 fuse in the underhood fuse block first.

(1)

HO2S - Bank 2 Sensor 1
(2)

HO2S - Bank 1 Sensor 1
(3)

HO2S - Bank 1 Sensor 2
(4)

HO2S - Bank 2 Sensor 2

That should have nothing to do with it. The p1825 if current, may be giving bad information as to what gear the vehicle is in, and defaults may be active. Hard to say.

The number one sensors may be accessed through the wheel wells, or from below. You may need some special purpose tools to get to them, like a 7/8" crowfoot socket, a flexible ratchet, and/or a wrench that has been fabricated(heated and bent) to suit the task. Following is the removal procedure for B2S1, bank 1 is similar less the air inlet grille.

Removal Procedure:
†Remove the left side air inlet panel. Refer to Air Inlet Grille Panel Replacement.
Notice: Refer to Oxygen Sensor Notice in the Preface section.

Important: Removal of the oxygen sensor is easier when the engine temperature is above 48°C (120°F).

†Disconnect the heated oxygen sensor (HO2S) electrical connector.
†Remove the HO2S electrical connector from the wiring harness bracket.
†Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle.
†Remove the HO2S.

As far as the IMS, it is in the transmission, and more than likely would require the lower valve body to be removed. It is driven by the manual shift shaft. I have never replaced one on a 5L30/5L40, but I would guess it is the same as the 6L80 that is in full size vehicles. I have changed several of those. I stand corrected, as I just looked at service information. The manual shaft has to be disassembled and withdrawn through the side as the switch rides on the shaft. Not necessarily a task I would suggest to a DIYer. Since it is that much of a task, I would recommend that you be certain it is at fault. It looks like the one that has turned your check engine light on, as told by the P0700. After replacement of you oxygen sensors, which if you replaced both number two sensors you have already addressed the P0056/P0036, clear the codes and see if it resets.