Transmission Diagnosis

Overheal

OK Motor experts and enthusiasts, I have a 2006 Jeep Grand Cherokee, about 116k miles on it. its got unevenly worn tires, bad rear rotors, a clinky front sway bar, but that's not even the most vexing problem.

This started happening about a month ago, shortly into a drive (<5 mins) the jeep would infrequently enter limp-mode where its stuck in 2nd/3rd gear and I can't manually override with the tiptronic handle. It starts happening when I get to a stop, only noticed it with brief stops (happened only 4 or 5 times so far) and the problem disappears when I restart the vehicle.

To help figure this out I bought a BlueDriver module, an OBD scanner, and it came up with this code that I could only find when I scanned the codes while the problem was active (aka didn't trip the engine light)

CODE P2767

Definition: Input speed sensor 2 circuit - no signal

Possible causes

• ISS 2 (N3) signal circuit is open
• ISS 2 (N3) signal circuit is shorted to another circuit
• ISS 3 (N3) signal circuit is shorted to ground/chassis
• ISS 2 ground circuit is open
• ISS ground circuit is shorted to another circuit
• ISS supply voltage circuit is open
• TCM has failed

Top Reported Fix: Replaced Transmission solenoid wiring harness

6 frequently reported fixes

• Replaces ABS Control Module/Hydraulic Control Unit (HCU)
• Replaced automatic transmission
• Replaced automatic Transmission connector
• Replaced Input Shaft Speed (ISS) Sensor
• Replaced Output Shaft Speed (OSS) Sensor
• Replaced Turbine Shaft Speed (Sensor Connector)

7 Other Reported Fixes

• Programmed TCM
• Repaired Automatic Transmission
• Repaired Automatic Transmission Connector
• Repaired Input Speed Sensor (ISS) Wiring)
• Repaired Transmission Wiring Harness
• Replaced TCM
• Replaced Transmission Speed Sensor

That output came from the BlueDriver app so I don't know what its credentials are. That said I was hoping someone here has transmission experience and could steer me in the right direction of the problems I should be looking for. Because the issue is relatively infrequent and corrects after a reboot I'm not convinced its a major issue like a TCM replacement; that said, it started doing this a month ago, it could just be the first symptom ahead of a major failure, but I don't know which. But If I ran to a shop with just this information, reading the error code, its an excuse to get shafted on the cost of essentially an entire rebuild of modules and sensors.



Now that I know what to hone in on though (electronics) I can datalog those if someone has an idea how I should interpret these outputs. Before I was convinced it was the hot weather that contributed, because its been over 100F out there, but this happened again tonight when it was quite a bit cooler and I was finally able to get the code. Above are the voltage readouts the vehicle supports, a sample log I began after I restarted the engine.

Thanks

Foxhole Norman

Get the fluid level checked, low ish fluid on auto gearboxes can cause a multitude of problems, one of them being holding gears.