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Notable Nissan diagnostics

Friday, December 1, 2017 - 09:00
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I often see the Nissan Murano, not because it is prone to problems but because it is a popular and reliable vehicle. Here are a few of the more interesting ones I’ve run into.

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Nissan Number 1

The first one is a 2007 Nissan Murano with 73,443 miles on it. It has a V-6 3.5L (VQ35DE) engine, which is standard on this platform. This vehicle is a FWD model but it also available in an AWD version as well. It came to us after having work done at another shop. The customer stated it was taken to them to have some oil leaks repaired on the engine and (here it comes) ever since getting the vehicle back the check engine light has been on. The customer stated they thought it wasn’t running the same since they got it back, but admitted it might be due to seeing the check engine light on and being overly sensitive because of that. 

A quick visual under the hood didn’t reveal much. It appears the other shop had done a decent job of repairing the oil leaks and putting everything back together correctly. While I was under the hood I also made a check on the condition and level of the engine oil (we’ll see why this is important in the next case study). Mostly I was looking for a connector that was unplugged thinking it would be a simple repair, but it was not going to be that easy.  A code scan was done and two codes were present, a P0021 “Bank 2 ‘A’ Cam Position Timing Performance” and a P0174 “Fuel System Too Lean Bank 2.” First thought was a vacuum leak due to either a gasket that was not installed correctly or a disconnected vacuum hose, but since I already did an underhood visual inspection I decided to observe scan data first. Banks 1 and 2 were both slightly lean with an Alpha of 105-107, which basically means the engine is 5 percent to 7 percent lean at idle. I wasn’t going to go look for a vacuum leak on the engine because, had there been one, the number would have been much higher. 

Figure 1

Thinking about the codes for a minute I realized whatever was causing the problem, it was going to be isolated to Bank 2 since both codes pointed in that direction.  Next I decided to look at data relating to the Cam Position Timing code and was surprised to see the variance between banks. The Intake Valve Timing for Bank 1 was -3° and the Intake Valve Timing for Bank 2 was 45° (Figure 1). The command for both Intake Valve Solenoids were 0 percent at idle (which is correct) so it was not a stuck solenoid holding the cam in the advanced position. However, that very well could be the cause of the lean code for Bank 2.

The last shop repaired oil leaks but the customer was not specific on exactly what they did. Was it an oil pan, valve covers, timing cover? Could they have removed a tensioner or the timing chain and the cam on Bank 2 jumped? Before going too much further and calling the customer for a list of exactly what was done, which should have been gathered by the service advisor when the vehicle was dropped off to us, I wanted to get a scope capture of the Crankshaft Position Sensor (CKP) and both Camshaft Position Sensors (CMP) to see if the data being displayed was really accurate. 

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To tell the truth

While the camshaft sensors are fairly easy to access on the top left side of each bank, the CKP sensor is a different story. Even with the vehicle on a lift the sensor is buried deep in the firewall side of the engine right where the bellhousing attaches to the engine. The best way to access the signal for testing is at the ECM itself, which is in the passenger compartment near the glove box. Similar to the sensors, the Bank 2 ignition coils are fairly easy to access while the Bank 1 coils are on the firewall side buried by the plenum. This is why the capture uses Cylinder #2 instead of Cylinder #1 as an ignition coil reference, but all signals could have easily been accessed at the ECM as well. A capture was taken and something did not look quite right with the Bank 2 CMP sensor (green trace on image). I compared this capture to a known good and it confirmed what the problem was. Both the CKP sensor and the Bank 1 CMP sensor were pulled from low to high, which is what the known good waveform showed; however the Bank 2 CMP sensor was flipped. The pulses were occurring at the correct time, just in the opposite direction (Figure 2). This was confusing the ECM as to the correct position of the Bank 2 Camshaft position and causing the data for the Intake Valve Timing PID to be off.

Figure 2

Looking closely at the Bank 2 CMP sensor revealed that it had recently been replaced. Contacting the customer and inquiring about the new CMP sensor, their receipt did not show that it was replaced. What I believed happened was the tech that was performing the work noticed that one of the oil leaks that needed to be repaired was the seal of the Bank 2 CMP sensor. Anyone that has disconnected a Nissan CKP or CMP sensor connector knows what I am referring to. The connector locking tab is spring loaded and removal requires first pushing the locking tab until it clicks, which will also hold the lock in that position, then pulling back on the connector housing to release it from the sensor. During this process, I think the tech tried remove the connector in the conventional way of pressing downwards on the tab and in doing so broke the CMP sensor.  Since it was the fault of the shop, an aftermarket sensor was ordered and installed without the customer knowing about it.

I installed a new OEM Camshaft Sensor for Nissan and took another scope capture, now the pattern looks correct (Figure 3). Also I noticed that the tech that installed the aftermarket camshaft sensor thought that sealing O-ring that came with the sensor wasn’t good enough so they applied a healthy amount of silicone where it attaches to the cylinder head.

Figure 3

Clearing the codes and watching the data PIDs for the Intake Valve Timing and Fuel Trims confirmed that the new sensor resolved the concern.

On to Nissan No. 2

The next case study is on a 2006 Nissan Murano S with 109,625 miles on the odometer, but the same V-6 3.5L (VQ35DE) engine as the previous vehicle. This was also a FWD similar to the last case study. The customers only complaint was a Service Engine Soon light being illuminated with no drivability complaints. A code scan revealed two codes in the ECM, a P1800 “VIAS Control Solenoid Valve Circuit Open” and P0011 “Bank 1 ‘A’ Cam Position Timing Performance.”

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