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P0918 is a diagnostic trouble code (DTC) for "Gear Shift Position Circuit – Intermittent Malfunction". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
In vehicles equipped with automatic transmissions, a P0918 code means that the powertrain control module (PCM) has registered an intermittent fault in the transmission shift mechanism range circuit, particularly in regard to a specific lever position. The PCM uses data from the transmission range sensor, in order to control engine RPMs, fuel metering, ignition timing and other drivability factors.
For most vehicles, a universal resistance level of 8 ohms is the norm in this particular circuit. Any fluctuation of greater than 10 percent (higher or lower) will result in a P2A00 code and an illuminated malfunction indicator lamp (MIL). Heater circuit voltage should be consistent with battery voltage, and any 10 percent fluctuation can result in a stored trouble code as well. Closed-loop O2 sensor readings that remain constant for 8 seconds or more can also result in a stored code and illuminated MIL.
In most cases, a P0918 code is due to a failed transmission range sensor or an out-of-adjustment transmission range sensor. The code is specifically for an intermittent problem, so in many cases a P0918 code is due to failed, loose, damaged or corroded wiring or contacts.
A technician will need a good quality OBD-II scanner/code reader and a digital volt/ohmmeter (DVOM).
Most vehicles, especially Ford models, are designed with a variable resistance transmission range sensor. This switch is located over the shaft for the transmission sensor, where the lever slides along a row of contacts. When the shift lever is moved, this range sensor pivots and is moved to different contacts.
The contacts send varying levels of resistance to the PCM, according to the position of the shift lever. The PCM reads these differing levels of resistance and voltage as the gear selected at the shifter, and acts on this information to determine shift points, engine ignition timing, fuel metering and other functions. The PCM also determines the proper gear for the transmission according to information on engine load, RPMs other factors.
Often, technicians replace the entire transmission range sensor when adjustment would have been sufficient. In some cases, technicians have even been known to condemn the transmission unnecessarily.
A P0918 code can prevent a transmission from shifting out of a gear, and can put the vehicle in limp-in mode, meaning it will barely be drivable at all.
Repair or replacement of:
A P0918 code can accompany recent transmission work. Check the range sensor’s wiring for corrosion or damage and check the sensor for proper adjustment. When installing the sensor, use thread locking compound to ensure the proper torque retention for the mounting bolts.
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