2002 Citroën Berlingo Manual Transmission with P0700, P1758, P1768 Codes - Is the Code Reader or PCM Faulty?

I recently purchased a 2002 Citroën Berlingo petrol model with a 1.4-litre engine. The engine light is on, and after using a code reader, I received several diagnostic trouble codes: P0700, P1758, P1760, and also P1298 and P0136. The P0700 code typically indicates an issue with the automatic transmission control system. However, my vehicle has a manual transmission (stick shift), so this code appears to be inconsistent with the actual drivetrain configuration. I'm wondering if my code reader is faulty or whether the Powertrain Control Module (PCM) might be malfunctioning. Additionally, I have P1758 and P1768 codes — these relate to transmission sensor faults, specifically related to gear position or shift solenoid operation. While I don't have official definitions for all of these codes in my manual, I suspect they may point to a faulty sensor or wiring issue. I also encountered P0118, which relates to an engine coolant temperature sensor reading -40°F (a value below the expected range). I replaced the sensor as there was a 5V signal present, but the new sensor still reads -40°F. This suggests either a faulty sensor or a deeper issue with the sensor circuit. Lastly, P0136 indicates an oxygen sensor fault in Bank 1 Sensor 2 — this has not been replaced yet and may be contributing to poor fuel efficiency or emissions. Could a malfunctioning sensor (such as the coolant temperature sensor) be affecting readings from other systems? I'm seeking advice on whether these codes are valid, what they mean for a manual transmission vehicle, and if any of them require immediate attention.