Intermittent gear indication problem
June 17th, 2024, 11:45 AM
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Intermittent gear indication problem
I have a 2011 Silverado 1500 with 4.3L V6 and 4L60e transmission that is experiencing intermittent gear indication problems on the dash. The truck has 74,000 miles on it.
I've went through the wire harness and looked for broken or cut shielding and inspected the plugs at the transmission and at the TCM. Aside from needing to install wire loom and electrical tape to dress of up the harness, no obvious issues have been found. The failure disappeared for about 2-3 weeks following movement of the wire harness, but the failure returned. I have since further inspected and moved the harness around, but failure continues intermittently. The failure is very erratic. It fails in drive and reverse and sometimes it holds steady, sometimes it drops in and out and sometimes it drops out for extended periods. Throughout the failures, it doesn't affect drivability, but it does affect the backup camera in reverse and when it fails in drive, it causes the cruise control to drop out. I do not get any trouble codes generated at this point.
Assuming there isn't something in the wiring I have missed, I'm down to the IMS or TCM. I watched a YouTube video where another person was having the loss of indication at the dash (like I'm having), but his truck was also in limp mode. His indication was in a hard failure though, unlike my failure.
The cost of the IMS switch and the TCM are about the same........$150. The TCM is easier and less intrusive, but I'm still leaning toward the IMS switch as the more likely candidate. I can't find the schematic online, so I'm still not clear how this circuit flows. In my mind, I place the truck into drive via the column mounted gear shifter, it uses a cable and linkages to actuate the shift lever on the side of the transmition, which rotates the selector shaft and causes the IMS to change position. The IMS switch sends a signal to the TCM informing it of the gear position and the TCM would then send a signal to the dash to provide a visual confirmation of the gear selected. I suppose the IMS could send a signal to the TCM and the dash (in parallel), but that seems less likely. It confuses me that the truck drives fine during a failure, but still affects reverse camera and cruise control function. Both the backup camera and the cruise control are aftermarket add-ons, so I'm not sure where they get their inputs from exactly.
Does the failure as I describe it eliminate one or the other component as a root cause?
Does anyone have any other suggestions beyond where I am looking?
I've went through the wire harness and looked for broken or cut shielding and inspected the plugs at the transmission and at the TCM. Aside from needing to install wire loom and electrical tape to dress of up the harness, no obvious issues have been found. The failure disappeared for about 2-3 weeks following movement of the wire harness, but the failure returned. I have since further inspected and moved the harness around, but failure continues intermittently. The failure is very erratic. It fails in drive and reverse and sometimes it holds steady, sometimes it drops in and out and sometimes it drops out for extended periods. Throughout the failures, it doesn't affect drivability, but it does affect the backup camera in reverse and when it fails in drive, it causes the cruise control to drop out. I do not get any trouble codes generated at this point.
Assuming there isn't something in the wiring I have missed, I'm down to the IMS or TCM. I watched a YouTube video where another person was having the loss of indication at the dash (like I'm having), but his truck was also in limp mode. His indication was in a hard failure though, unlike my failure.
The cost of the IMS switch and the TCM are about the same........$150. The TCM is easier and less intrusive, but I'm still leaning toward the IMS switch as the more likely candidate. I can't find the schematic online, so I'm still not clear how this circuit flows. In my mind, I place the truck into drive via the column mounted gear shifter, it uses a cable and linkages to actuate the shift lever on the side of the transmition, which rotates the selector shaft and causes the IMS to change position. The IMS switch sends a signal to the TCM informing it of the gear position and the TCM would then send a signal to the dash to provide a visual confirmation of the gear selected. I suppose the IMS could send a signal to the TCM and the dash (in parallel), but that seems less likely. It confuses me that the truck drives fine during a failure, but still affects reverse camera and cruise control function. Both the backup camera and the cruise control are aftermarket add-ons, so I'm not sure where they get their inputs from exactly.
Does the failure as I describe it eliminate one or the other component as a root cause?
Does anyone have any other suggestions beyond where I am looking?
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