Incorrect speedometer reading?

I absolutely could not afford the 8-hour job to replace the input and output sensors in the transmission. I sent in my gauge cluster to be repaired as I have several indicator lights that don't come on during the indicator light test when you first start the truck, and I hoped maybe my speedometer issue maybe was there somehow. My cluster came back completely gone through with a note from the repair guy that it was already completely functioning, but they went through it anyways. My mechanic put it back in and I still don't have most of my indicator lights. A test drive showed the speedometer still off. He reached out to GM and the tech was not at all sure why my speedometer was off his only suggestion was to try re-setting the ECU. When plugged in to do so it showed green checks for everything, but my mechanic still checked all and reset it. My speedometer is now correct. However, I still don't have most of my indicator lights including the check engine light. Is there an easy way to test/check to find the cause of them not lighting up during the indicator lights test?

I absolutely could not afford the 8 hr job to replace the input and output sensors in the transmission. I sent in my gauge cluster to be repaired as I have several indicator lights that don't come on during the indicator light test when you first start the truck and I hoped maybe my speedometer issue maybe was there somehow. My cluster came back completely gone through with a note from the repair guy that it was already completely functioning but they went through it anyways. My mechanic put it back in and I still don't have most of my indicator lights. A test drive showed speedometer still off. He reached out to GM and the tech was not at all sure why my speedometer was off his only suggestion was to try reseting the ecu. When plugged in to do so it showed green checks for everything but my mechanic still checked all and reset it. My speedometer is now correct. However I still don't have most of my indicator lights including the check engine light. Is there a easy way to test/check to find the cause of them not lighting up during the indicator lights test?