Code 731

Hi all,

My father has been having trouble with his 99 Caravan. 3.3 Liter. The gauges began to act erratic and the door locks cycle. The speedometer swings from left to right, along with the gas gauge. It is currently in "limp Mode" (won't shift passed 2nd gear). The transmission was replaced by the dealer ~2 years ago. This problem began recently.

After reading the forum a few times I recommended he take it to Autozone to have the trouble codes pulled. I also recommended he reset the computer after scanning the codes, to see if it would reset untill he could get it repaired.

He reset the computer before scanning the codes and the problem remained, still not shifting and the check engine light came back on within a few blocks. The only code that was found was a "731- gear 1 incorrect ratio" per the person at Autozone.

Any ideas? Any help would be greatly appreciated. Unfortunatly I only know what I have stated here as we live some distance apart and I have not seen any of this first hand. Thanks Again.

Greg

I had a similar problem when my transmission went bad. Take the car to a transmission shop and have them check it out. It may be a simple problem but mine cost $1700 for a new transmission.

I had a similar problem when my transmission went bad. Take the car to a transmission shop and have them check it out. It may be a simple problem but mine cost $1700 for a new transmission.


Thanks GTP Dad.

Anyone else have ideas? I'd like to do as much for him as I can, and help him to keep the trans shop honest....

Greg

Well if i had to take my best guess i would check the VSS. If I’m not mistaken your vehicle doesn’t have a speedometer cable. It uses a signal generator in the transmission that creates an electrical signal in relationship to vehicle speed called a Vehicle Speed Sensor (VSS). This information is processed by the vehicle’s computer for engine and transmission management and provides the signal for the body computer that controls the speedometer. If the VSS is failing it will not always set a code in the computer. Why? It all depends on how it is failing (lying). Also you have to know that the computer in many vehicles have a programmed speed limiter. The computer’s program uses vehicle speed as an input and if a specified speed is seen by the computer it will cut the fuel injectors to prevent the vehicle from going too fast. Knowing this, and the fact that your engine starts running rough when the speedometer flips out at 100 plus MPH, I’d say fuel cut out is kicking in. For this to happen it is likely that the Vehicle speed Sensor is on its way out. Before it quits it’s going you make your life difficult. Have your technician plug into the vehicle computer and monitor the vehicle speed sensor signal. It’s likely your problem is an intermittently lying Vehicle Speed Sensor.However,the ECMs are normally programmed with base guidelines to go by in case of sensor failure.

On the other hand,you may not be able to shift out of second because of the fact that you are running on these base settings.

I would start by replacing the Vehicle Speed Sensor, then disconnect the battery cable for 30 seconds to reset the ECM, then run the trouble codes again. This may solve your problem.

Thanks hernandez3674, he got it. I suggested replacing the input and output vehicle speed sensors. He did just the output and the problem is gone. The CEL turned off after two trips also.

Greg