![]() ![]() At first, everything was fine, but as the vehicle warmed up on the test drive, I noticed that the overdrive pressure switch would activate in 2nd gear. I hooked up a scan tool, put it in graph mode to monitor the switch. Recently I had a 42RLE come in with an overdrive pressure switch rationality code set. There’s a few different things that can cause these codes, hydraulic leaks in the valve body or case, the switch in the solenoid pack, the connectors, pins in the connectors, shorted wires, or even a failed computer. This code means that either the switch is not responding, or the switch is activated when it’s not supposed to be on. One of the most common codes that appear in many Chrysler transmissions is the pressure switch rationality code. When the switch is activated, it provides ground and the computer sees the change in the voltage, and determines the switch has closed. The relay provides battery voltage through a three hundred ohm resistor to the pressure switches in the solenoid pack (figure 1), this voltage is fed back to the computer to monitor the state of these switches. In most Chrysler transmissions, a solenoid is turned on or off to control fluid flow in a circuit to a clutch, and the pressure switch monitors the existence of pressure in that circuit, to verify the solenoid has done it’s job. For most Chryslers, these pressure switches are used to verify pressure in a circuit that is being operated by the solenoids. Late GM front wheel drives and many other manufacturers used them to monitor shift valve positions. Some early GM’s used them for determining position of the manual valve, some used them for determining position of the lock up valve. And, ALWAYS check the condition of the fluid.Many transmissions by various manufacturers use pressures switches to monitor the presence of fluid in a circuit. This accomplishes 2 things, I'm isolating the sensor from the wring harness and checking the quality of the connector and it's connection. I generally back probe the Range Sensor, so I bypass any of the harness wiring. The next step is to start doing pinpoint tests i.e voltage drops and continuity tests of the Transmission Range Sensor. If the Range Sensor is giving erroneous information to the TCM/PCM, then you may have located a problem that could set the P0706 code. Watch the scan data to see if the Range Sensor is reporting accurate information to the TCM and PCM. Start out from a dead stop and gently accelerate. When diagnosing a P0706 code, it is important to record the freeze frame information and then to duplicate the code setting conditions with a test drive at speeds around 15-35 mph. ![]() This is an irrational (or impossible) condition, that is, how could the vehicle be going 25 mph and be in park? For example, say the vehicle is going 25 mph, as reported by the vehicle speed sensor, but the Range Sensor is reporting that the transmission is still in park. When the code P0706 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is not seeing a clear, rational change in the data sent from the Transmission Range Sensor, especially after the vehicle is in motion. P0706 Diagnostic Theory for Shops and Technicians NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smogĬO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas In some cases, there may be performance problemsĬommon Problems That Trigger the P0706 Codeĭefective Transmission Range Sensor (PRNDL input)ĭefective Transmission Range Sensor (PRNDL input) wiring or connectorĭirty transmission fluid that restricts the hydraulic passages In unusual cases, there are no adverse conditions noticed by the driver It is attached directly to the manual valve of transmission, so when the shift lever is moved say from park to drive, the Transmission Range Sensor communicates this critical information to the above mentioned vehicle computer systems. The Transmission Range Sensor (also referred to as the PRNDL input and/or neutral safety switch) tells the transmission control module (TCM) and the powertrain control module (PCM) that the transmission is in park, reverse, neutral, drive, low, 2nd, 3rd etc. ![]() The purpose of the automatic transmission is to match the engine's optimum power and torque characteristics to the driver's desired rate of acceleration and speed by auto-selecting different gear ratios or 'speeds' to power the wheels. OBD-II Code P0706 is defined as a Transmission Range Sensor Circuit Range/Performance
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