Guide To P0790 OBD Error Code Solutions

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It is important to understand the meaning of the OBD code that is flashing. P0790 is a generic OBD-II code, related to the powertrains for an issue with voltage or resistance with the transmission mode controller. Basically, the signal that is being sent isn’t in sync with the parameters set by the manufacturer for the specific vehicle. When this problem occurs, it will basically restrict the powertrain control module or the PCM from allowing the “power mode”. It is this power mode that allows the transmission to shift later and downshift earlier as per the requirement of the driver.

The P0790 code is stored by the Powertrain module, when there’s a fault in the transmission. Usually there will also be other related codes that stored with this code, and it is important that those should be diagnosed first and also repaired before proceeding to diagnosing P0790 error.

What causes this problem with the Normal/Performance Switch Circuit Malfunction?

• Defectiveness or damages of the switch
• Corrosion which may be causing high resistance like connectors, pins, grounds, etc.
• Wiring is showing multiple issues like frayed, open, short to power, short to ground, etc.
• Defectiveness in the lever of the shift
• Malfunction of the TCM (Transmission Control Module)
• Issue with the Fuse/box

1. Transmission Connector - Try to observe the connector closely and see if the damages can be reversed via repairs. If not, you will have to opt for a new connector, you can order them online with Parts Avatar, we provide a wide range of brands compatible with your vehicle and price point.
2. TCM - You may be able to resolve the P0790 problem via repairs, otherwise you can buy a new replacement online. It’s easy and shipping is free for orders valuing over CAD $99.
3. Transmission Switch - Be careful while repairing the switch, it is a very important component and replacement may solve your problem permanently. Don’t worry, just order online with Parts Avatar, and have your order delivered within few days!
4. Scanner - Get the best quality scanning tools from Parts Avatar. We ship to the remotest corners of Canada, so don’t worry and order now and solve your P0790 error.

It is essential to know the symptoms of an issue as only then you would be able to solve the problem. So that’s why we have listed out some major symptoms of OBD Code P0790 here:

Common Symptoms

When this P0790 code is set, it will either make the vehicle to stay in normal mode or the transmission will go into “limp-mode”. Going into limp-mode reduces the speed of the vehicle enough that it can make it to the repair ship with minimal damage. In such a situation the overdrive light may also turn on.

• Mode switch is not operative
• Haphazard and/or atypical switch operation is noticed
• Shift pattern is not efficient
• Power is low
• Transmission is not downshifting when torque is required

Here are some ways with the help of which you will be able to correct the OBD Code P0790

The most common repair options for error P0790 are as follows:

• Clean the transmission mode switch
• Replace the transmission mode switch
• Repair damaged wiring for the transmission mode switch

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Diagnosis of OBD codes requires patience, and correct information. Here are some easy steps which you should follow in order to diagnose this fault code:

Basic Step - 1 If your diagnostic scanner has the capability to check data stream, you would be able to monitor values and/or operation of your switch (normal/performance). For this you will have to toggle the switch on and off and see if the scanner is able to recognize the inputs. You may experience a delay here, but that’s normal, and you should be patient at this step, in fact a few seconds lag is is also good during monitoring of switches.

When trying to figure out the situation of the circuits with an inoperative mode switch, you will have to jump some pins at the modes switches connector and be able to rule out the circuit. Now if you have been able to rule out no problems with the circuit, but the switch remains to be inoperative, then you will have to test the switch itself. For this step, you will need your vehicles manual, and match up your vehicle’s specifications to the code and symptoms and follow the specifications and procedures. You may require a moderately able scan tool too.

Basic Step 2 - In this step, you will be testing the switch, commonly these switches are present only to signal the appropriate module/s like the TCM, Body Control module (BCM), ECM, PCM, etc. so there are chances that it shows modified patterns of shifting. A lot of these tend to be of on/off style, which means that you can use an DVOM meter and run a simple continuity test and determine the functionality of the sensor. Using your multimeter, ensure you research which connectors/pins you need to monitor, as these sensors are at times incorporated into the shift lever.

Common Mistakes When Diagnosing the P0790 Code

Many mechanics may wrongly report that the switches weren’t damaged as much as they were corroded, and they may proceed to cleaning them and replacing them but that’s not a wise solution.