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.
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.
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| 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.
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| 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.
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| 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.”
The P0011 Camshaft Position Timing Performance code is one that is familiar to most technicians and what the “performance” part of the code means is that it is not operating as expected by the PCM. As with almost all Camshaft Position Timing codes the first step is to check the medium responsible for changing the camshaft timing, the engine oil. With insufficient oil supply, the actuators cannot move or hold the cams in the desired position. On several occasions I have seen techs replace solenoids, actuators, phasers and so on due to these types of codes without ever checking the level and condition of the engine oil. This Murano was no exception; the dipstick had only a trace of oil on it when removed from the port on the front cylinder head. It actually took 2.5 quarts of oil to bring it to the upper section of the crosshatch area and this is on a vehicle that during an oil and filter change specifies an initial fill of 4.2 quarts. Restarting the vehicle and using the bidirectional controls of the scan tool I was able to control the position of the intake cams and saw that both banks were responding equally to the commanded percentage of solenoid activation (Figure 4). I didn’t take a before capture of the bidirectional controls for the simple reason that low engine oil level is such a common cause of this code that I would only start looking elsewhere if correcting the oil level did not repair the concern.
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| Figure 4 |
Now onto the second code, the P1800 VIAS Control Solenoid fault. This is actually my first time seeing this particular code. VIAS stands for Variable Intake Air System. Anyone who is into performance tuning can attest to the benefits of this type of system. The Nissan Variable Intake System uses a solenoid, which either allows or blocks vacuum to a power valve which in turn controls the effective length of the intake runners. At medium speed (around 1800 RPM) the ECM grounds the VIAS solenoid valve, which allows engine vacuum to reach the power valve actuator. The actuator then closes the power valve, increasing the distance the incoming air must travel between the throttle body and the intake valve. When the engine is at a very low or high speed, the ECM turns off the VIAS solenoid blocking engine vacuum to the power valve actuator. This allows the power valve to move to the normally open position which shortens the incoming airflow’s path to the intake valves.
The reasoning behind the variable intake length is to maintain power across a broader engine operating range. By having a longer runner length at lower and medium engine speeds torque is increased. However, at higher engine RPMs the longer runner length diminishes the available torque output. By using a butterfly valve to block off the extended length runner and providing a shorter airflow path to the intake valve at higher engine speeds, the incoming air velocity is increased and torque output is regained.
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| Figure 5 |
My first time
Since I am not familiar with this code I used a popular automotive technical website to get some testing insight on the system. It stated that there is no actual resistance specification given by Nissan, but an expected resistance of the VIAS solenoid valve is 25-40 ohms. Alright, this is an easy test so I ohmed out the solenoid and the meter showed 33 ohms (Figure 5), right in the middle of the specification so the solenoid is ok right? A popular saying of one of the smartest technicians I know is, “If you ohm a component and it tests bad, it’s bad. However if you ohm out a component and it tests good, it could still be bad.” Bottom line, if you ohm test a component and it tests good, test it another way to confirm.
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| Figure 6 |
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| Figure 7 |
An easy connection of my PicoScope with the Blue trace showing the voltage supplied by the ECM Relay and the Green trace showing the ground command from the ECM was established and a vacuum gauge was installed (Figure 6) in place of the power valve actuator. Normally you would need to raise the RPM to get the ECM to activate the solenoid but using the bidirectional controls of a scan tool it can be accomplished with the vehicle running at idle. Activating the VIAS solenoid the first couple of times showed that the ECM was commanding the solenoid on and off (Figure 7), also the solenoid was responding correctly by applying and blocking vacuum respectively. However, about the fourth or fifth time of turning the solenoid on and off I noticed the vacuum gauge did not move. The scope showed that the ECM driver had supplied ground to the solenoid, but when deactivated, the solenoid did not have a clean turn off, but more of a stepped pattern back up to system voltage (Figure 8). I noticed this occurred each time that the solenoid was commanded on but did not allow vacuum to pass through it. The VIAS solenoid valve was sticking occasionally, however this did not show up on an ohms test.
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| Figure 8 |
A new VIAS solenoid was installed and the codes cleared. After a long test drive no codes were present or pending and the Murano was returned to the customer along with a maintenance recommendation and a reminder to check their oil level routinely.