Error 18 on Nissan Elgrand: decoding, diagnostics and repair

Error code P0340 (or simply "error 18") on Nissan Elgrand - one of the most common problems faced by owners of these minivans, especially models E50 And E51 with engines VQ25DE, VQ35DE or QR25DE. This error is related to camshaft chain and can indicate both minor malfunctions in the sensor and serious mechanical failures. It cannot be ignored: if ignored for a long time, the risk of damaging the engine increases significantly.

In this article we will look in detail at what exactly it means. error 18, what symptoms accompany it, how to correctly diagnose the problem (including working with a diagnostic scanner and multimeter), and what to do to fix it - from simply rebooting the computer to replacing the sensor or timing chain. You will also find unique data on typical “jambs” of repairmen, which only aggravate the problem, and tips for prevention.

What does error 18 mean on Nissan Elgrand?

Error P0340 (in diagnostic systems Nissan often shown as "18") stands for "Camshaft Position (CMP) Sensor Circuit Malfunction". This sensor is responsible for synchronizing the operation of the injectors and ignition system with the camshaft position. If the ECU (electronic control unit) does not receive the correct signal, the engine becomes unstable or stalls altogether.

On Elgrand error 18 can appear in two scenarios:

• 🔴 Constantly — “Check Engine” is on, the engine is running rough, losing power or won’t start.
• 🟡 Periodically — the error appears during a cold start, at high speeds or after washing the engine, then disappears.

It is important to understand that P0340 is not always the fault of the sensor itself. The reasons may lie in:

• 🔌 Problems with wiring (breakage, oxidation, short circuit).
• ⚙️ Mechanical wear of the timing chain or its tensioner.
• 🖥️ Malfunctions in the ECU or firmware.
• 🛢️ Contamination of oil channels (relevant for VQ35DE).

⚠️ Attention: If error 18 is accompanied by a knocking sound in the engine or a metallic clanging sound - turn off the engine immediately. This may indicate a timing chain jump, which leads to a collision of pistons with valves and a major overhaul.

Symptoms of error 18 on Elgrand

In addition to the "Check Engine" light, the error P0340 is manifested by the following symptoms:

Symptom	Probable Cause	Danger level
The engine does not start or stalls immediately after starting	Complete loss of signal from the CMP sensor or timing phase shift	❌ Critical
Floating idle speed (500–1500 rpm)	Unstable sensor signal, dirty contacts	⚠️ Average
Loss of power, failures during acceleration	Incorrect operation of the ignition system due to synchronization failure	⚠️ Average
Increased fuel consumption (+1–3 liters per 100 km)	The ECU goes into emergency mode, enriching the mixture	⚠️ Low
Knocking or clanging noise in the timing belt area	Chain stretch, tensioner or damper wear	❌ Critical

On Elgrand E51 with engine VQ35DE error 18 is often accompanied by error code P0345 (bank 2 camshaft sensor circuit malfunction). This is due to the features of the VVT ​​(variable valve timing) system, which uses two sensors - one for each camshaft.

Reasons for error 18

To accurately determine the source of the problem, you need to consider all possible causes as a whole. Below is an expanded list with clarifications for Nissan Elgrand:

1. Problems with the camshaft position (CMP) sensor

The sensor may fail due to:

• 🔥 Overheating (located next to the manifold outlet).
• 💧 Oil or antifreeze gets on the contacts.
• 🕳️ Mechanical damage (for example, when replacing a valve cover).

On Elgrand CMP sensor is located top right on the cylinder head (if you look in the direction of travel). It can be identified by a single 3-pin connector.

2. Wiring faults

A common problem is broken or shorted wires between the sensor and the ECU. Particularly vulnerable places:

• 🔌 Sensor connector (oxidation, poor contact).
• 🚗 Wiring harness near the exhaust manifold (melts due to temperature).
• 🔧 Place of entry of the tourniquet into the salon (grinding).

3. Mechanical problems with timing belt

If the sensor and wiring are in order, but the error remains, the culprit is mechanical wear:

• 🔗 Timing chain stretching (critical for mileages >150 thousand km).
• 🛠️ Wear of the chain tensioner or damper.
• ⚙️ Phase shift due to incorrect installation of camshafts.

⚠️ Attention: On Elgrand E50 with engine VQ25DE The timing chain is considered “eternal”, but in practice its resource rarely exceeds 200 thousand km. After this run, the risk of teeth breaking or skipping increases sharply.

4. Problems with the ECU or firmware

Less commonly, error 18 occurs due to:

• 🖥️ ECU malfunction (for example, after disconnecting the battery).
• 📱 Incorrect firmware (relevant after chip tuning).
• 🔋 Poor contact in the control unit connectors.

How to check the ECU on Elgrand?

To diagnose the ECU you will need a scanner (for example, Launch CReader or ELM327). Connect to the OBD-II connector (located under the steering wheel on the left) and check:

1. The presence of other errors (for example, P0335 - crankshaft sensor).

2. Real-time CMP sensor signal parameters (must be stable at idle speed).

3. On-board network voltage (should be 12–14 V).

Diagnosing error 18: step-by-step instructions

To accurately determine the cause of the error, follow this algorithm. Let's start with the simplest checks:

Step 1: Reset the error and check for a floating defect

Sometimes error 18 appears due to a temporary glitch. To check this:

1. Connect the diagnostic scanner and reset errors.
2. Start the engine and let it run for 5-10 minutes.
3. If the error returns, go to step 2.

Step 2: Checking the CMP Sensor

For this you will need multimeter:

1. Disconnect the sensor connector.
2. Call the contacts for a break:
   • Resistance between pins 1–2 there must be 500–1500 Ohm.
   • Resistance between any terminal and ground - infinity (no short circuit).
3. Check the voltage at the connector (with the ignition on):
   • Between +12V (pin 3) and the mass should be 12 V.
   • Between the signal wire (pin 2) and ground - 0 V (with the engine not running).

Step 3: Timing Chain Diagnosis

If the sensor is working, but the error remains, check:

• 🔗 Chain tension: with a weak tension it can slip by 1-2 teeth.
• 🛠️ Status of sedatives: Cracks or chips cause the chain to vibrate.
• ⚙️ Tag Match on the camshafts and crankshaft (see repair manual Elgrand).

To visually inspect the chain, you will need to remove it. valve cover. On VQ35DE This can be done without removing the intake manifold, but you will need a special wrench to secure the camshafts.

Step 4: Checking the ECU and Firmware

If all the previous steps did not work:

• Connect the scanner and check crankshaft sensor (CKP) parameters. If the signal from it is also unstable, the problem may be in the ECU.
• Try it reflash the block standard firmware (for example, via Nissan DataScan).
• Check ECU weight — oxidation of contacts often leads to failures.

How to fix error 18: from simple to complex

Depending on the cause, repair methods range from basic to capital-intensive. Below are step-by-step solutions with cost and complexity estimates.

1. Error reset and ECU adaptation

If the error appears after disconnecting the battery or chip tuning:

• Clear errors via scanner.
• Follow the procedure ECU Reset (available in the menu of most diagnostic devices).
• Let the engine idle for 10-15 minutes to learn.

Cost: 0 rub. (if you have a scanner).

2. Replacing the camshaft position sensor

If the sensor is faulty:

1. Buy a new sensor (original number for Elgrand E50/E51 — 23731-AL500 or 23731-4M500).
2. Disconnect the connector and unscrew the fastening bolt (10mm wrench).
3. Install the new sensor, tighten the bolt to torque 8–10 Nm.

Cost: 1,500–3,000 rub. (sensor) + 500 rub. (work).

3. Wiring repair

If the problem is in the wires:

• Clean and crimp the contacts in the sensor connector.
• Replace the damaged section of the harness (use heat shrink tubing for protection).
• Check the ground of the sensor - it should be attached to the cylinder head without rust.

Cost: 300–1,000 rub. (materials).

4. Replacing the timing chain and tensioner

If the chain is stretched or has slipped:

• Remove the front engine cover (a special tool is required to secure the camshafts).
• Replace the chain, tensioner, guides and seals (kit for VQ35DE costs ~15,000 rubles).
• Align the timing marks according to the manual (an error of 1 tooth leads to error 18!).

Cost: 20,000–35,000 rub. (with work).

⚠️ Attention: On Elgrand with engine VQ35DE When replacing the timing chain, be sure to check the condition VVT phase regulators. Their jamming is a common reason for the reappearance of error 18 after repair.

Typical repair mistakes

Many owners Elgrand They are faced with the fact that after repair, error 18 returns. This is due to common errors:

1. Incorrect installation of the CMP sensor

The sensor must be installed with gap 0.5–1 mm to the camshaft toothed disc. If the gap is larger, the signal will be weak; if it is smaller, the sensor will quickly fail.

2. Ignoring the condition of the timing chain

Often they only change the sensor or tensioner without checking the chain. On Elgrand With a mileage of >150 thousand km, the chain is almost always stretched and requires replacement.

3. Failure to comply with tightening torques

When replacing the timing chain, the camshaft sprocket bolts must be tightened to 80–100 Nm. Over-tightening leads to deformation, under-tightening leads to slippage.

4. Use of non-original spare parts

Non-original CMP sensors (for example, Chinese counterparts) often give an incorrect signal. The same applies to timing chains - cheap sets stretch after 30-50 thousand km.

Prevention of error 18 on Nissan Elgrand

To avoid problems with the camshaft sensor and timing chain:

• 🔧 Change oil and filter every 7–10 thousand km (especially important for VQ35DE with VVT system).
• 🔊 Follow extraneous sounds from the timing belt area (clanging, rustling - signs of chain wear).
• 🚗 Check once every 100 thousand km chain tension (even if it is “eternal”).
• 💧 Avoid engine pressure wash — water gets into the sensor connectors.
• ⚡ Use voltage stabilizer when “lighting up” to avoid ECU failures.

On Elgrand E51 after 2010, it is recommended to clean the contacts of the CMP and CKP sensors every 2 years with a special spray (for example, CRC Electronic Cleaner). This prevents oxidation and signal loss.

FAQ: Frequently asked questions about error 18

Is it possible to drive with error 18?

Short-term - possible, but not recommended. The engine runs in emergency mode, which leads to:

• Increased fuel consumption (+2–3 l/100 km).
• Accelerated wear of the catalyst.
• Risk of collision of pistons with valves (if the chain has slipped).

If the error is accompanied by a knocking sound - the car cannot be driven.

How to reset error 18 without a scanner?

You can reset the error by turning off negative battery terminal for 10–15 minutes. However, this will not eliminate the cause, but only temporarily hides the problem. After 2-3 engine starts the error will return.

On Elgrand with the system Nissan Intelligent Key disconnecting the battery may require retraining the keys (procedure Key Relearn).

How much does it cost to diagnose error 18 in the service?

The cost depends on the region and level of service:

• Basic diagnostics (scanner + sensor check) - 1,000–2,000 rubles.
• Advanced Diagnostics (check timing, wiring, ECU) - 3,000–5,000 rubles.
• Due diligence (with removal of the valve cover) - 5,000–8,000 rubles.

On Elgrand with engine VQ35DE It is recommended to order immediately complete timing belt diagnostics, since error 18 is often related to the circuit.

Can error 18 appear after replacing the timing chain?

Yes, and this is a personal situation. Reasons:

• Incorrectly displayed timing marks (1 tooth error).
• Not replaced dampers or tensioner.
• Used non-original chain low quality.
• Not reset ECU adaptation after repair.

Solution: double-check the marks and quality of spare parts, perform ECU Reset.

What other errors can appear along with P0340?

On Nissan Elgrand error 18 is often accompanied by:

• P0335 — malfunction of the crankshaft position sensor (CKP).
• P0011/P0021 — problems with the VVT system (phase regulators).
• P0171/P0174 — lean fuel mixture (the computer incorrectly adjusts the fuel supply).
• P0300 - random misfires (due to incorrect synchronization).

If errors are on along with P0340 P0011/P0021, the problem is almost certainly timing chains or phase regulators.