If your Honda’s check engine light is on and the scanner shows a specific transmission-related code, you’re probably wondering what it means. This article explains exactly what is P1706 Honda engine code, its causes, and how to fix it.
This code is specifically about your vehicle’s transmission, not the engine itself, but it’s stored in the engine control module. It points to a problem that needs your attention to keep your Honda running smoothly.
What Is P1706 Honda Engine Code
The P1706 code stands for “Transmission Range Switch Circuit Malfunction.” In simpler terms, it means the car’s computer is getting a signal from the transmission range switch that it doesn’t understand or finds implausible.
This switch is also commonly called the neutral safety switch or the transmission position sensor. It’s a crucial component that tells the engine control module (ECM) or powertrain control module (PCM) what gear you’ve selected—Park, Reverse, Neutral, or Drive.
That information is used for many things. It controls the backup lights, prevents the car from starting in any gear other than Park or Neutral, and helps the computer adjust engine performance for smooth shifting.
How the Transmission Range Switch Works
The switch is physically connected to the transmission’s shift shaft. When you move the gear selector, the shaft turns and changes the electrical circuits inside the switch.
Each gear position (P, R, N, D, 2, 1) creates a unique combination of electrical signals. The car’s computer reads this combination to know exactly what gear you’re in. A P1706 code triggers when the signal is missing, erratic, or doesn’t match the computer’s expectations.
Common Symptoms of a P1706 Code
You’ll likely notice more than just a check engine light. Here are the typical signs:
- Illuminated Check Engine Light (MIL): This is the first and most common indicator.
- Transmission Shifting Problems: The transmission may shift harshly, at the wrong time, or refuse to shift at all. It might default to a “limp mode” (often 2nd or 3rd gear) to protect itself.
- Gear Indicator Mismatch: The gear shown on your dashboard (P, R, N, D) doesn’t match the actual gear the car is in.
- Starting Issues: The car might not start, or it might start in a gear other than Park or Neutral because the computer doesn’t know the correct position.
- Backup Light Failure: Your reverse (backup) lights may not come on when you shift into Reverse.
- Stalling at Idle: The engine might stall when you shift from Park to Drive or Reverse.
Main Causes of the P1706 Honda Code
Several issues can lead to this fault code. Here are the most frequent culprits, starting with the simplest.
1. Low or Contaminated Transmission Fluid
This is a common and often overlooked cause. The transmission range switch is mounted on the transmission and relies on proper fluid levels for overall hydraulic health. Low fluid can cause pressure problems and erratic signals.
Old, burnt fluid full of debris can also interfere with the switch’s operation or clog related passages.
2. A Faulty Transmission Range Switch
The switch itself can wear out or fail internally. The electrical contacts inside can become corroded, worn, or damaged from heat and vibration over time. This is the most direct cause of a P1706 code.
3. Electrical Wiring and Connector Issues
The problem might not be the switch, but the path to it. Look for:
- Damaged, frayed, or broken wires leading to the switch.
- Corroded or loose electrical connectors at the switch or the PCM.
- Poor electrical grounds that disrupt the signal circuit.
4. Problems with the PCM (Powertrain Control Module)
While less common, the computer module that processes the signal could have an internal fault. This is usually a last-resort diagnosis after everything else has been checked.
5. Mechanical Linkage Problems
On some older Honda models with automatic transmissions, a physical cable or linkage connects the gear shifter to the transmission. If this is out of adjustment, damaged, or binding, it can prevent the range switch from being in the correct position.
Step-by-Step Troubleshooting Guide
Always start with the simplest and safest checks first. You’ll need a basic OBD-II scanner and a multimeter for some steps.
Step 1: Check and Scan for Codes
Use your OBD-II scanner to confirm the P1706 code is present. Clear the code and take the car for a short test drive. If the code returns immediately, you have a hard fault. If it takes a while to return, the issue might be intermittent.
Also, check for any other codes (like P0705, P0706). Multiple transmission codes can point to a wiring or PCM issue.
Step 2: Inspect the Transmission Fluid
- Park the car on a level surface with the engine running and the transmission warmed up.
- Pull the transmission dipstick (for models that have one), wipe it clean, reinsert it fully, and pull it out again.
- Check the fluid level. It should be between the “Low” and “Full” marks.
- Assess the fluid condition. It should be reddish and relatively clear, not dark brown/black, burnt-smelling, or full of metal particles.
If the fluid is low, top it up with the correct Honda ATF. If it’s contaminated, a fluid change or flush may be necessary, but diagnose the root cause first.
Step 3: Visual Inspection of Wiring and Connectors
Locate the transmission range switch. It’s usually on the side of the transmission case, connected to the shift shaft.
- Carefully trace the wiring harness from the switch back towards the firewall.
- Look for any obvious damage, chafing, or burnt wires.
- Disconnect the electrical connector at the switch. Check for corrosion (green or white powder), bent pins, or signs of moisture.
- Clean the connector with electrical contact cleaner and reconnect it securely.
Step 4: Test the Transmission Range Switch
This requires a multimeter. You’ll need to check the switch’s resistance or continuity across different pin combinations in each gear position. The exact procedure and values vary by model year.
- Consult a service manual for your specific Honda to find the correct pinout and resistance specifications.
- With the connector disconnected, set your multimeter to measure resistance (Ohms).
- Place the probes on the specified switch terminals for each gear position (P, R, N, D, etc.).
- The resistance should change or show continuity/open circuit as specified for each gear. If the readings are incorrect or show an open circuit in all positions, the switch is faulty.
Step 5: Check for Voltage and Signal at the PCM
If the switch tests good, the problem might be in the wiring to the PCM. With the connector plugged back in and the ignition ON (engine off), use your multimeter to check for reference voltage and ground at the switch connector.
You may need to back-probe the connector carefully. If power and ground are present but the signal isn’t reaching the PCM, there’s a break in the signal wire.
Step 6: Inspect Shift Linkage/Cable Adjustment
For applicable models, check the mechanical linkage. Have an assistant move the shifter inside the car while you watch the lever on the transmission. Every shifter position should correspond precisely to the lever’s position.
If there’s slack or misalignment, the linkage may need adjustment or replacement.
Repair and Replacement Guide
Once you’ve identified the cause, here’s how to adress it.
Replacing the Transmission Range Switch
- Disconnect the negative battery terminal for safety.
- Locate the switch on the transmission. You may need to remove other components for access.
- Disconnect the electrical connector.
- Unscrew the mounting bolts (often one or two). The switch will slide off the shift shaft.
- Before installing the new switch, compare it to the old one. Ensure the shaft seal is in good condition.
- Installation is the reverse. Important: The new switch must be aligned correctly. Sometimes the car must be in a specific gear (often Neutral) during installation. Refer to your vehicle’s manual.
- Reconnect the battery, clear the codes, and test.
Fixing Wiring Problems
For damaged wires, cut out the bad section and solder in a new piece of wire of the same gauge. Always use heat-shrink tubing to insulate the connection properly. Never just use electrical tape in the engine bay.
Addressing PCM Issues
Suspecting a bad PCM is a major step. It often requires professional diagnosis with advanced scan tools to rule out everything else. Replacement PCMs usually need programming to match your vehicle’s VIN and immobilizer system.
Prevention Tips
To avoid a P1706 code and other transmission issues:
- Follow Honda’s recommended schedule for transmission fluid changes. This is often every 30,000 to 60,000 miles under severe use.
- Regularly check the transmission fluid level and condition.
- Address any minor shifting issues or electrical gremlins promptly before they lead to bigger problems.
- Keep the engine bay clean and protect electrical connectors from excessive moisture.
Frequently Asked Questions (FAQ)
Can I drive my Honda with a P1706 code?
It’s not recommended. The car may be in a fail-safe “limp mode,” which limits gear usage and power to protect the transmission. You could cause further damage or experience sudden stalling or an inability to shift. Have it checked as soon as possible.
How much does it cost to fix a P1706 code?
Costs vary widely. A new transmission range switch part costs between $50 and $200. With labor, a shop might charge $150 to $400. If wiring repair or a PCM is needed, costs can rise to $500 or more.
Is the P1706 code serious?
Yes, it should be considered serious. It affects the transmission’s operation, your ability to start the car safely, and key functions like backup lights. Ignoring it can lead to being stranded or causing internal transmission damage.
Can a bad battery cause a P1706 code?
Indirectly, yes. A weak battery or poor charging system can cause low voltage that makes sensors, including the range switch, send erratic signals to the PCM. Always ensure your battery and alternator are in good health when diagnosing electrical codes.
What’s the difference between P1706 and P0705?
P0705 is “Transmission Range Sensor Circuit Malfunction (PRNDL Input).” They are very similar and often related. P0705 typically indicates a more general circuit problem, while P1706 is a sub-code that often points more specifically to the switch or its direct signal. They are often diagnosed and fixed using the same process.
Dealing with a P1706 code in your Honda can be frustrating, but it’s often a fixable issue. By starting with simple checks like fluid level and wiring, you can potentially solve the problem yourself or at least provide valuable information to your mechanic. Remember, prompt attention to transmission codes is key to avoiding more expensive repairs down the road and keeping your Honda reliable for years to come.