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2008 Dodge Grand Caravan P0716 P0721 P0791 P0740: Transmission Stuck in Neutral, TCM Failure Suspected

Model: 2008 Dodge Grand Caravan Fault Code: P0716 Posted: 2016-11-20 22:49

We own a 2008 Dodge Grand Caravan with the 3.8L V6 engine and 62TE transmission. While driving on the interstate yesterday, the vehicle suddenly acted as if it were in neutral—no response to gear shifts, neither drive nor reverse. The onboard diagnostic system has triggered multiple transmission-related codes: P0716 (Transmission Input Speed Sensor A Circuit Range/Performance), P0721 (Transmission Input Speed Sensor B Circuit Range/Performance), P0791 (Transmission Over-temperature Condition), and P0740 (Transmission Coolant Temperature Sensor Circuit). Given that these are all part of the transmission control circuit, it's raising concerns about a potential failure in the Transmission Control Module (TCM). The vehicle is stock with no aftermarket electrical modifications. We have a diagnostic scanner and confirmed the codes via scan. Wiring harness inspection showed no visible damage or corrosion. However, we've observed that the transmission linkage is physically moving—indicating the gear shift mechanism is active but not engaging properly. We’ve cleared the codes, which did not return, yet the vehicle still fails to engage gears. Could this point toward a faulty solenoid or internal transmission issue? Any insights from owners with similar experiences?

Related fault codes
P0716P0721P0791
Comments (9)
Anonymous 2016-11-21 08:32

Could you clarify your engine and transmission setup? Are there any aftermarket electrical components installed? Do you have access to a diagnostic scanner? Have you checked the wiring harness for input, output, and transfer speed sensors?

Anonymous 2016-11-21 08:36

This is a 3.8L V6 paired with the 62TE transmission. No aftermarket electronics or modifications—fully stock configuration. We do have a diagnostic scanner and successfully retrieved all codes using it. The wiring harness has been thoroughly inspected, and no signs of damage or wear were found.

Anonymous 2016-11-21 08:59

I just confirmed that the transmission linkage is physically moving—this indicates the transmission is attempting to shift gears, even though it fails to engage properly in drive or reverse.

Anonymous 2016-11-21 11:39

Try retrieving and documenting the freeze frame data for each code (P0716, P0721, P0791, P0740). After clearing codes, start the vehicle and monitor input sensor voltage (ISS)—this is located at the top of the transmission. The other sensors are lower but grouped together. Since these sensors generate AC voltages, ensure your multimeter is set to AC mode when measuring. Also, check for any additional diagnostic codes. I would expect more than just these if there’s a significant fault.

Anonymous 2016-11-21 11:43

We cleared the codes and have not seen them return since. However, the vehicle still won’t shift into gear. Could this be due to a faulty solenoid or internal transmission failure? No other diagnostic codes are present.

Anonymous 2016-11-21 14:55

What specific data was recorded in the freeze frame for each of the P0716, P0721, P0791, and P0740 fault codes? This information is critical to diagnosing whether the issue stems from sensor misreading or a deeper transmission problem.

Anonymous 2016-12-01 09:40

I’ve seen a similar case on a 1998 Grand Caravan SE with a 3.3L engine—P0740 and P0700 codes appeared only after the alternator failed and the battery was completely discharged. These codes may remain dormant for years before reactivating under low charging conditions. If your vehicle has been experiencing intermittent issues, it’s possible that a charging system failure triggered the fault. As a note: can you adjust the drive cycle to avoid triggering the P0740 check engine light? For example, by limiting speed or avoiding overdrive use during testing?

Anonymous 2017-03-29 20:43

Did you ever find a solution for your Grand Caravan’s transmission issue? We’re experiencing the same symptoms.

Anonymous 2017-03-29 20:53

We did. The vehicle was towed to a Dodge dealership where they performed an ignition recall. During that visit, they inspected the transmission and charged $161 just to remove the pan bolts. They then stated the transmission was 'shot' and offered either a full replacement for $6,000 or a trade-in value of around $500. After researching independently, we took it to a smaller shop that replaced the transmission with a remanufactured unit—same model as the dealership’s—complete with a 3-year/100,000-mile warranty for only $3,200. It now operates perfectly. My advice: don’t accept high repair quotes from dealerships. Shop around and get competitive pricing—especially when it comes to transmission replacements. We ended up getting the same transmission as the dealership but at half the cost.