Full guide: Finding and fixing no spark on a Nissan Murano Z50

The situation when Nissan Murano the second generation (Z50 body) stops starting due to lack of spark, and is one of the most difficult to quickly diagnose. The owner is faced with the fact that the starter vigorously turns the engine, but starting does not occur, and various errors may light up on the dashboard, which do not always indicate the direct cause of the problem. Unlike simple mechanical failures, lack of spark on VQ35DE or VQ35HR V6 engines is often associated with electronic failures that require an in-depth understanding of the engine management system.

Ignition system on Murano Z50 built according to the scheme of individual ignition coils integrated into the tips of the spark plugs. This solution minimizes energy losses, but creates certain risks during diagnostics. If you observe a complete stop of all cylinders, the problem most likely lies in common elements of the system: the crankshaft position sensor, the ignition control module, or the ECU itself. Ignoring this problem and trying to start the engine blindly can lead to gasoline getting into the catalyst and its expensive replacement.

Primary diagnostics: Checking the crankshaft position sensor

The first and most critical element from which to begin troubleshooting is crankshaft position sensor (DPKV). Without a signal from this device, the electronic control unit does not understand exactly when to spark and inject fuel. If the DPKV fails or its wiring is damaged, the protection system instantly blocks the operation of the ignition coils and the engine will not start.

On the VQ35 engine, the sensor is located at the bottom of the cylinder block, often in a hard-to-reach location near the flywheel or crankshaft pulley. Vibrations typical of powerful naturally aspirated motors can, over time, loosen the fastening or damage the insulation of the wires. Checking the sensor resistance should be carried out with a multimeter with the connector disconnected. Typically, the resistance should be in the range from 500 to 1000 Ohms, but the exact values ​​depend on the year of manufacture and modification of the engine.

• 🔍 Visually inspect the sensor connector for oxidation or traces of oil, which often gets onto the contacts due to seal leaks.
• ⚡ Check the integrity of the wiring harness from the sensor to the ECU, looking for frayed areas, especially in bend areas.
• 📉 Compare the resistance readings of the new and old sensor to eliminate performance drift.

If the sensor is working, but there is no spark, you need to check for the presence of a signal at the coil connector. To do this, you can use an oscilloscope or a special spark tester. The absence of control pulses when the starter rotates indicates a problem in the control circuit or the control unit itself.

⚠️ Warning: Do not try to start the engine for more than 10 seconds at a time without a break. This can cause the starter to overheat and drain the battery, making further diagnostics more difficult.

Analysis of the operation of ignition coils and spark plugs

When the signal from the crankshaft sensor is confirmed, the next step is to check the ignition coils. On Nissan Murano Z50 coils with integrated spark plugs are installed, which form a single module. The failure of one coil usually leads to a loss of power and misfire in a particular cylinder, but failure of all at once or failure of the control module for them requires a different approach.

Often the problem lies not in the coils themselves, but in their connectors or high-voltage circuits. Oxidation of contacts in spark plug pads can block the passage of a high-voltage discharge. It is recommended to remove all six coils, clean the contacts and check for a spark on each of them by holding them close to the engine ground while cranking the starter.

• 🔥 Check the spark plug wells for oil or coolant that could cause a short circuit.
• 🔌 Inspect the coil connector clamps, as they often break and the contact becomes unreliable.
• 🛠️ Use a known good coil to test on different cylinders to rule out local failure.

It is important to note that sometimes coils may look good on the outside, but become internally broken under load. In such cases, without a stand or oscilloscope, it is difficult to accurately determine the faulty element. If one or two coils do not produce a spark, but the rest work, the problem is local. If there is no spark on any of them, look for the cause in the general power or control circuits.

Problems with the engine control unit (ECU)

The most difficult and expensive scenario is a malfunction of the electronic control unit (ECU). Ignition control unit on Murano Z50 integrated into the main engine computer. If the unit is not receiving power, has damaged internal control keys, or a software failure, it will not be able to generate a spark.

A common problem is the failure of power transistors inside the ECU, which are responsible for switching the coils. This can happen due to a power surge, a short circuit in the wiring, or simply aging components. Diagnostics requires connecting a professional scanner to read data from the CAN bus and check the availability of blocks.

Component	Symptoms of a problem	Verification method
Crankshaft sensor	No signal on the scanner	Multimeter, oscilloscope
Ignition coils	No spark on a specific cylinder	Spark tester, replacement
ECU block	No connection to scanner, power error	Checking the voltage at the connector
Ignition relay	No power to coils	Relay click test, multimeter test

If, when checking the power supply, there is voltage at the ECU connector, but there is no connection with the computer, this is a sure sign of the death of the unit. In some cases, the problem can be solved by replacing the unit with a used one and reflashing it for a specific car (VIN code).

⚠️ Attention: When replacing the ECU with a used one, be sure to ensure that the immobilizer chip (NATS) is compatible or disabled. Otherwise, the engine will stall immediately after starting.

Immobilizer and NATS system

Anti-robbery system NATS (Nissan Anti-Theft System) on Murano Z50 may cause no spark if it does not recognize the key. In this case, the starter will turn the engine, but the ECU will block the supply of fuel and spark. This is a common problem when using duplicate keys or after the key battery has died.

If the lock or key light on your dashboard is flashing and the engine won't start, the problem is almost certainly a security system problem. Sometimes the system operates falsely due to poor contact in the immobilizer antenna located around the ignition switch.

• 🔑 Try using a spare key to rule out a chip failure in the main key.
• 📡 Check the antenna around the ignition switch for broken wires or damage.
• 🔋 Replace the battery in the key if it is dead, as a weak signal may not be read.

To reset an immobilizer error, sometimes it is enough to reconnect the key through a diagnostic scanner. If the antenna is damaged, replacing the entire steering column may not be necessary; replacing the antenna itself is sufficient.

What to do if the key is lost?

If the only key is lost, you will have to replace the entire ignition switch and all cylinders, or reprogram the ECU by disabling the NATS system, which requires specialized equipment and skills.

Wiring and Connectors: Hidden Enemies

On cars with a mileage of more than 100,000 km, the main problem is not the components themselves, but their connections. Oxidation contacts in the ignition coil or sensor connectors can lead to a complete lack of spark. Moisture protection on connectors Nissan Over time, it loses its properties, and water or condensation gets inside.

Particular attention should be paid to the wiring harness running from the engine to the passenger compartment and to the fuse box. Metal elements in the engine compartment can wear through the insulation, causing a short to ground. This often happens where the harness passes through body partitions.

To check the integrity of the wiring, use the multimeter's continuity mode. Check every wire from the coil connector to the ECU connector. If the resistance in the circuit is infinitely large, it means the wire is frayed or broken.

⚠️ Warning: Do not use tape or tape to temporarily repair wires under the hood. Use only heat shrink tubing and high-quality insulation that is resistant to high temperatures.

Step-by-step troubleshooting algorithm

To avoid guessing and changing parts at random, follow a strict diagnostic algorithm. Start by checking the simplest thing: fuses. If all fuses are normal, proceed to diagnosing sensors and signals.

1. Check for power supply to the ignition coils (should be 12V when the ignition is on).

2. Check the signal from the crankshaft sensor (pulses).

3. Check the control signals from the ECU to the coils.

4. If there is power and signals, but there is no spark, the problem is in the coils.

5. If there are no signals, the problem is in the computer or the wiring to it.

Accurate diagnostics will require access to an OBD2 diagnostic connector and software capable of reading real-time data. Conventional scanners can only show errors, but not the dynamics of sensor operation.

Specifics of VQ35DE and VQ35HR engines

VQ series motors installed on Murano Z50, have their own characteristics. The HR (High Response) version has a more complex valve timing control system (CVTCS), which also affects the ignition operation. If the phase shifters do not work correctly, the ECU may block starting.

It is also worth considering that on these motors the wiring of the phase sensor often fails, which indirectly affects the spark. Unlike older engines, there is no ignition distributor, and all the logic for spark formation lies with the electronics.

• 🔧 Check the phase sensor (CMP), as its malfunction may block starting.
• ⚙️ Check the operation of the variable valve timing system by ear and through a scanner.
• 🌡️ Make sure the engine temperature is correct, as some systems block starting at extreme temperatures.

If the problem cannot be solved by standard methods, the control unit may need to be reflashed or replaced. In some cases, “reflashing” to a more recent version of the software helps, which eliminates software bugs in the ignition control.

Why can't you start an engine without a spark?

: If there is no spark, but fuel is supplied, gasoline will flow into the cylinders, washing away the oil film. This will lead to water hammer or scoring in the cylinders during subsequent startup.

Why does my Nissan Murano Z50 lose spark only in cold weather?

In cold weather, condensation inside connectors and coils can freeze or change their dielectric properties, causing breakdown. Also, in cold weather, contact resistance increases, which can be critical for old components.

Is it possible to drive if only 3 cylinders are running?

No. Driving on three cylinders leads to excessive fuel consumption, destruction of the catalyst due to unburned gasoline and increased vibrations, which can destroy engine mounts and attachments.

How much does it cost to diagnose a lack of spark?

The cost of diagnostics varies from 2000 to 5000 rubles, depending on the service and equipment. A full diagnostic with an oscilloscope and ECU check may cost more, but it will save money on replacing unnecessary parts.

What to do if the ECU unit burns out?

It is necessary to replace the unit with a similar one (with the same VIN or reprogrammable). It is often more profitable to restore an old unit in a specialized service, replacing burnt components, than to buy a new original one.

Is it possible to check the coils without removing them from the engine?

It is partially possible by checking for a spark through the spark plug well, but for a complete check and visual inspection of the coil contacts it is better to remove it. This also allows you to check the condition of the spark plugs.