How frustrating it is when on a hot summer day, as you go to open a nice cold can of your drink of choice, and the tab breaks off? You are outside, away from any tools to remedy the problem quickly. It now requires a MacGyver mentality looking around at the resources available to get to that nice cold drink. As frustrating as this can be, it’s even more frustrating when a broken tab requires a rebuilt transmission to be removed to be fixed.
This recently happened at two different shops on the same day. Ed from Affordable first called in to the ATSG help line with a 2018 Grand Caravan with a P0706 code for a Transmission Range Sensor Rationality problem. This sensor has four wires going to it with reference voltage in them supplied by the PCM/TCM called the C1, C2, C3 and C4 circuits (see Figures 1 and 2).
A PID showing the open and closed status for each of these circuits is provided in a scan tool. The sensor is designed in such a way as to close these circuits by grounding them in a set sequence (Figure 3).
Take the C1 circuit for example: This wire will be grounded, closing the circuit in Park and Neutral only. All the other ranges will be open (Figure 4).
When each of these circuits were inspected, technicians discovered that the C2 circuit always remained open. It should be grounded in all ranges except OD and 3. This typically would indicate that the wire to the sensor is broken so the sensor is unable to ground the circuit. A bad connection would be another possibility. After inspecting the C2 circuit, it was discovered that there was something wrong with the sensor itself. This required pulling the unit and valve body to gain access to this sensor. It was then that Ed discovered a tab that holds the circuit housing to the detent plate was missing the retaining tab. Figures 5 and 6 show the location of this retaining tab.
It is designed to hold the circuit housing in place, so the circuit fingers seen in Figure 2 maintains tension contact to the detent plate. When this tab is broken, it compromises the tension for the C2 circuit. Figures 7 and 8 are the pictures Ed provided showing the missing tab with his sensor.
No sooner did this take place that another call came in from Chevy at Auto Trans Matic having the exact same issue with his 2016 Grand Caravan. We sent the pictures we received from Ed to him. Chevy verified with us the next day that his sensor suffered from the same broken retaining tab. This makes it an important inspection process to be put in place to avoid all of this undesirable extra work.