So your check engine light (CEL) is on. As you probably know, it can light up for all sorts of reasons. But since the introduction of OBD-II back in the 1990s, many of those reasons are stored in a standardized set of diagnostic trouble codes that can be accessed with a generic code reader.
The good thing about the CEL and the entire OBD-II engine management and diagnostic system is that it takes a lot of the guesswork out of what's actually going on with a vehicle's engine and drivetrain. A tech can connect a code reader to the OBD-II port and quickly access any trouble codes that are stored in the engine computer, pointing him or her in the right direction for diagnosis and repair.
Note: Code scanning is one of the free services at your local Advance Auto Parts store.
Where it can get tricky, though, is interpreting what the trouble codes mean. Your car's check engine light doesn't just indicate a trouble code from the engine—it can also mean transmission issues.
Trouble code P0705: Transmission Range Sensor Circuit Malfunction — What it Means
Every transmission is equipped with a range switch that sends a signal to the powertrain control module (PCM) indicating whether the transmission is in park, drive, neutral or reverse. The range switch delivers a specific voltage for each transmission range, which the PCM is then able to determine. When the PCM is receiving a reading that's not logical or is out of spec, the P0705 code is registered and the check engine light is illuminated.
Symptoms
- No-start condition
- Transmission PRNDL indicator on dash isn't illuminated
- Erratic shifting behavior
- No reverse lights
- Transmission shift lever has to be wiggled for vehicle to start
What Happens If I Ignore It?
In many cases, you won't be able to ignore a P0705 code because you won't be able to start your vehicle. For safety reasons, vehicles can only start when the transmission is in park or neutral, so if the PCM doesn't know which gear it's in, it won't start. You might also not be able to shift gears, or shifting may be erratic.
Possible Fixes
In most cases, a P0705 code is caused by the range sensor itself. That's not always the case, though. This code can also be caused by a slight misalignment of the switch, sending an erroneous reading to the PCM, or there could be a problem somewhere else in the circuit.
The first step for diagnosing any transmission problem is to check the fluid level and condition of the fluid, and a P0705 code is no exception. If the fluid looks good, locate the range sensor and inspect it for road debris, corrosion, damage to the wiring or any other obvious problems. If no problems are indicated, it's time to take a multimeter and check voltages from the range sensor as an assistant puts the vehicle in each gear. You'll need to refer to a shop manual to find the right voltage range for your unit.
If a problem with the switch is what you determine, replacing the switch can remedy it but there may be other adjustments specific to your vehicle as well. Also bear in mind that P0706, P0707, P0708, and P0709 can all be related trouble codes that accompany P0705.
Have you come across this trouble code? Let us know in the comments.
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About the Author(s)
Jerry Renshaw is a veteran journalist, gearhead and guitar player, and cultivated his mechanical skills by 30 years of turning wrenches to keep one piece of junk or another on the road. He's owned everything from a Chevette to (three) minivans to a fire-breathing Dodge muscle truck, and is constantly keeping up to speed on what's going on in the automotive world.
