Nissan Titan Starts In Drive
So I have a strange one here. I was called to program a Nissan Titan Transmission. The customer complaint was that the vehicle would start in any gear position. In checking the calibration, it belonged to a 2004 Titan. Checking with the dealer, the calibration should be 31000-ZH21A. It had 31000-7S604 loaded. The loaded calibration was for a 2004 model and this is a 2005. I force flashed the correct calibration to see if it would correct the problem. The vehicle still starts in every gear but reverse. (I am assuming that it is the same problem) There is a code P0615 which is a problem with the starter relay. The repair information states this happens when the engine will start outside of neutral or park. The gear symbols light properly as the shifter is moved from gear to gear. The Neutral safety switch has four leads that go to the transmission control module. It appears that these four leads signal which gear the lever is in. Since the vehicle will not start in Reverse, the wire from the TCM to the relay must be functioning correctly. This also suggests that the relay is working correctly. The logical explanation I can see is that the TCM is faulty or that the TCM is the wrong hardware for the 2005. Since I do not have a good description of the 4 wires between the Neutral safety switch and the TCM, I hate to condemn the TCM if it is something else. Have any of you seen this issue before?
I have a question for your question. How does one get the wrong calibration on a TCM? A "tune" that someone did? Someone previously flashed it improperly?
My bet would be used transmission or tcm was installed to get around the flash requirement of these transmissions, TCMs come blank and are inside the transmission IIRR
Michael Berg is correct. There is evidence the transmission has been replaced with a used one.
The inhibit circuit is built into the IPDM (CPU) on this vehicle. That this is happening between the original transmission and the new/used transmission with the incorrect calibration that is now correct. I believe the starter relay is doing what its supposed to do. However i feel the IPDM may be the culprit here. I can send the checks for the circuit if you need via email. But from what i read this is happening between 2 separate transmissions same symptom.
I get where you are coming from. The rub I have with the IPDM theory is that the state of the inhibit circuit is changing between reverse and forward gears. My understanding is that the signal (power or ground) from the TCM is what allows the relay to energize. So what is happening is that the TCM recognizes the gear position but is not cutting the signal to the relay in forward gears, only in reverse. If the TCM cuts the signal, there is no way for the IPDM to energize the relay. The circuit would be open. If I understand the workshop manual properly, the code P0615 is set because the TCM is sending an enable signal when it should not be there. I would appreciate the checks for this. My email ….
I sent the checks to your email you provided. In Park or Neutral gears the starter relay should display "on" and the selector in any other position should display "off". However in any forward gear position it stays "on" allowing the vehicle to start.. if the gear selector is changing and you can see the gear selector changing via scan tool. That the transmission was replaced could that wire be damaged or crushed... yes. However i think you would have the same issue in any and every gear.. that its relegated to the forward gears only is telling me the IPDM may not care to inhibit in any forward gear when it should. Just seems very sketchy to me that 2 different transmissions are having the same exact issue before they called you to rescue them