Nissan Murano Won't Start Push Button

Alright, let's dive into diagnosing a frustrating problem: your Nissan Murano's push-button start system refusing to cooperate. A "no-start" condition with a push-button ignition can stem from a variety of sources, ranging from simple fixes to more complex electrical issues. This guide aims to walk you through the troubleshooting process, assuming you have a moderate level of mechanical and electrical knowledge. We'll cover common culprits and provide step-by-step checks.

Understanding the System: Key Components

Before we start probing wires, let's briefly review the key components involved in the Murano's intelligent key (iKey) and push-button start system:

• Intelligent Key (iKey) Fob: This transmits a unique radio frequency (RF) signal to the vehicle, authenticating your authorization to start.
• iKey Antenna System: These antennas, typically located inside the cabin (e.g., dashboard, center console), receive the signal from the iKey. The closer the iKey is to an antenna, the stronger the signal.
• Body Control Module (BCM): The BCM is a central control unit that manages various electronic functions, including receiving and processing the iKey signal. It acts as a gatekeeper for the starting system.
• Engine Control Module (ECM): Also known as the Powertrain Control Module (PCM), the ECM controls engine operation, including fuel injection and ignition timing. The BCM signals the ECM to allow starting.
• Push-Button Start Switch: This switch initiates the starting sequence once the iKey is authenticated. It provides the signal to the BCM.
• Starter Motor: The electric motor that cranks the engine to initiate combustion.
• Battery: The source of electrical power for the entire system. A weak battery is a common cause of starting problems.
• Brake Switch: This switch, located at the brake pedal, tells the system the brake is depressed. This is a safety requirement for starting the vehicle in most modern systems.

Preliminary Checks: The Low-Hanging Fruit

Always start with the simplest and most common potential problems. These are the things that often get overlooked:

1. Battery Voltage

A weak battery is the prime suspect. Even if the lights come on, the battery may not have enough amperage (cold cranking amps - CCA) to turn the starter motor. Use a multimeter to check the battery voltage at the terminals.

A fully charged battery should read around 12.6 volts. Anything below 12.0 volts is a sign of a weak battery. Have the battery load tested at an auto parts store to confirm its condition. They'll put a heavy load on it to see if the voltage drops excessively.

2. iKey Battery

The iKey relies on a small coin cell battery to transmit its signal. A dead or weak battery can prevent the system from recognizing the key. Try replacing the battery in your iKey with a new one. Consult your owner's manual for the correct battery type (usually a CR2032 or similar). After replacement, attempt to start the vehicle.

3. iKey Proximity and Interference

Ensure the iKey is close to one of the interior antennas. Try holding it near the steering column or the center console. Also, be aware of potential radio frequency interference. Mobile phones, laptops, or other electronic devices close to the iKey or the receiver antennas can sometimes disrupt the signal. Move these devices away and try again.

4. Brake Pedal Switch

The Murano requires the brake pedal to be depressed before the engine can be started. The brake light switch signals this to the BCM. To test this:

1. Ensure the ignition is OFF.
2. Locate the brake light switch near the brake pedal.
3. Have someone observe the brake lights while you press and release the pedal. If the brake lights don't activate, the switch could be faulty.
4. You can use a multimeter to test the continuity of the switch. Disconnect the connector and use the multimeter in continuity mode. When the pedal is depressed, the switch should show continuity (a closed circuit). When released, it should be open.

5. Steering Wheel Lock

Sometimes, the steering wheel lock mechanism can engage and prevent the starting system from functioning properly. Try gently wiggling the steering wheel back and forth while pressing the start button. This might release the lock.

Advanced Troubleshooting: Diving Deeper

If the simple checks don't solve the problem, we need to investigate further into the electrical system. Warning: Work safely. Disconnect the negative battery terminal before performing any electrical testing to prevent short circuits and potential damage.

1. Checking Fuses and Relays

Blown fuses are a common cause of electrical problems. Consult your owner's manual for the location of the fuse boxes and the fuse diagram. Check the fuses related to the starting system, iKey system, BCM, and ECM. Look for broken filaments inside the fuse. Replace any blown fuses with the correct amperage rating.

Relays act as electrical switches, controlling higher current circuits with lower current signals. A faulty relay can prevent power from reaching the starter motor. The starter relay is often located in the engine compartment fuse box. You can try swapping the starter relay with an identical relay from another non-critical system (e.g., horn relay) to see if that resolves the issue. If it does, replace the faulty relay.

2. Diagnosing the Starter Motor

If the starter motor is faulty, it won't crank the engine. To test the starter motor:

1. Locate the starter motor, usually mounted on the engine block near the transmission.
2. Have an assistant turn the ignition key to the "start" position.
3. Listen for a clicking sound from the starter solenoid. A click indicates the solenoid is engaging, but the motor might be failing.
4. If there's no clicking sound, use a multimeter to check for 12V power at the starter solenoid terminal when the key is in the "start" position. If there's no power, the problem lies upstream (wiring, relay, or BCM).
5. If there is power, but the starter doesn't engage, the starter motor or solenoid is likely faulty and needs replacement.

Bypass Test: A *careful* bypass test can confirm a faulty starter. (Warning: Extreme caution needed. This involves directly connecting the battery to the starter, bypassing all safety interlocks. Have a fire extinguisher nearby.) Connect a heavy-gauge jumper cable directly from the positive (+) terminal of the battery to the small terminal on the starter solenoid. If the starter engages and cranks the engine, the starter itself is good, and the problem lies elsewhere in the starting circuit.

3. BCM and iKey System Diagnostics

This is where things get more complex and often require specialized equipment. The BCM controls the iKey system, and if there's a problem with the BCM or the communication between the iKey and the BCM, the engine won't start.

• Scanner/OBD-II Reader: Use a diagnostic scanner or OBD-II reader to check for trouble codes (DTCs) related to the iKey system, BCM, or ECM. These codes can provide valuable clues about the problem. Common codes might include "Key Not Detected," "BCM Communication Error," or "Immobilizer Fault."
• iKey Antenna Testing: The iKey antenna system can be tested using a Nissan-specific diagnostic tool. The tool can measure the signal strength of each antenna and identify any faulty antennas. A weak or non-functioning antenna can prevent the BCM from recognizing the iKey.
• BCM Programming: In some cases, the BCM may need to be reprogrammed or reflashed with updated software. This is usually done by a qualified technician with access to Nissan's diagnostic software.
• iKey Registration: If the iKey has been lost or damaged, a new iKey needs to be registered with the BCM. This process typically requires a Nissan-specific diagnostic tool and security access.

4. ECM Issues

Although less common than BCM or iKey problems, the ECM can also prevent the engine from starting. The ECM needs to receive a signal from the BCM confirming that the iKey is valid before it will allow the engine to start. If the ECM is faulty or has corrupted data, it may not recognize the BCM signal.

Diagnostic codes related to the ECM can point to specific problems. In some cases, reflashing or reprogramming the ECM may be necessary. This is best left to a qualified technician.

Recap & Final Thoughts

Diagnosing a "no-start" issue with a push-button ignition system can be challenging, but by following these steps, you can systematically identify the root cause of the problem. Remember to start with the simplest checks first and progress to more complex diagnostics as needed.

Important Note: Modern vehicle electronics are complex, and some diagnostic and repair procedures require specialized tools and expertise. If you're not comfortable performing these tasks yourself, it's best to consult a qualified technician. Trying to fix the issue without the right tools or knowledge can potentially damage the system further.

Good luck with your troubleshooting!