J-PIPES & GESI CATS (COBB GREENSPEED)
P0171 is thrown if AF Correction or AF Learning exceed +35% for more than 10 seconds during two consecutive drive cycles.
99% of the time p0171 means you have a vacuum leak in the system.
If the fuel trims are +35% during idle/cruise AND wide open throttle, the leak is in between the MAF sensor and the turbo.
If the fuel trims are +35% during idle/cruise BUT -35% at wide open throttle, the leak is after the turbo and before the engine.
The most common causes of vacuum/boost leaks:
- intercooler couplers popping off
- charge pipe couplers popping off
- EBCS lines popping off
- EBCS line hitting exhaust & melting a hole in it
- BPV line popping off
- BOV piston stuck open due to hardened oil/grime on the piston not allowing it to move
- low pressure fuel pump has popped out of place
Main Issue w/ Boost Leaks
- Whenever a silicone coupler is leaking or a pipe pops off, the blow-by oil in the system gets between the silicone coupler and the pipe. If you just slide the pipe back into place and tighten the clamp, the pipe will just keep sliding off because there is oil in-between the coupler and pipe.
Properly Fix the Leak
- The silicone coupler and pipe need to be taken apart and thoroughly cleaned with MAF cleaner or rubbing alcohol to remove the oil.
- Once the surfaces are oil free, then they can be re-installed.
- If you have a "problem pipe" that just keeps popping off, you can try spraying some hairspray on the pipe before you connect the coupler. The hairspray will help them stick together.
Be Prepared - Tools, Rags, Flashlight, etc.
- Keep the necessary tools in the trunk to deal with intercooler couplers popping off, charge pipes popping off, EBCS & BPV lines popping off, etc. All of these are common issues.
P0172 is thrown if AF Correction or AF Learning exceed -35% for more than 10 seconds during two consecutive drive cycles.
99% of the time p0172 means you have one of two issues:
1) Water or oil on the MAF sensor element. This is caused by
2) Moisture in the MAF connectors or MAF extension cable connectors. This is caused by
P0137 is thrown if you have moisture/water in the rear 02 sensor connector, an exhaust leak near the sensor or a cut wire between the rear 02 sensor and ECU.
Water in the rear 02 sensor connector is caused by:
P0137 Fix:
This CEL comes on when fuel is leaking around the o-rings on the LPFP and leaking back into the fuel basket. Since there is a leak, the fuel pressure will continually drop below 200 psi and will eventually throw the CEL.
The LPFP needs to be removed and the o-rings inspected. The LPFP needs to be re-installed with the stock white spacer and 2 o-rings.
This is not a HPFP issue.
This CEL comes on when fuel is leaking around the o-rings on the LPFP and leaking back into the fuel basket. Since there is a leak, the fuel pressure will continually drop below 200 psi and will eventually throw the CEL.
The LPFP needs to be removed and the o-rings inspected. The LPFP needs to be re-installed with the stock white spacer and 2 o-rings.
This is not a HPFP issue.
This CEL comes on when fuel is leaking around the o-rings on the LPFP and leaking back into the fuel basket. Since there is a leak, the fuel pressure will continually drop below 200 psi and will eventually throw the CEL.
The LPFP needs to be removed and the o-rings inspected. The LPFP needs to be re-installed with the stock white spacer and 2 o-rings.
This is not a HPFP issue.
** PLEASE READ THIS BEFORE BLINDLY REPLACING YOUR HPFP or LPFP BECAUSE PEOPLE ON FB SAID IT’S THE ISSUE. IT IS EXTREMELY RARE FOR EITHER OF THE PUMPS TO FAIL. **
It is normal for the fuel pressure to occasionally drop down to ~150 psi on throttle lifts. If you have fuel pressure on the AP gauge screen 24/7, then you may occasionally see values below 150 psi.
If the fuel pressure is dropping below 150 psi every single time you let off the throttle and/or constantly dropping down to 30-50 psi, then there is an issue that needs to be addressed.
Low fuel pressure CEL's only happen for 4 main reasons:
1) LPFP O-Ring Leak
- Fuel is getting around the o-rings on the low-pressure fuel pump nipple and leaking back into the fuel basket. This type of leak will present itself in several different ways depending on the severity of the leak:
- Small Leak - random pressure drops down to 100-200 psi. These mainly occur when you let off the throttle after a wide open throttle pull. It is difficult to diagnose a small leak as random pressure drops are not un-common. All you can really do is monitor the fuel pressure and if the pressure drops become more frequent and drop to lower and lower psi, then the data is pointing to this leak. This leak will not likely throw a CEL because the pressure drops do not occur for a long enough period of time.
- Large leak - when the leak has progressed or an o-ring is torn, then the pressure will continually drop to 25-50 psi on throttle lifts. Once the leak has reached a certain point the fuel pressure will just start tanking down to 500 psi between 5,000-6,500 rpm. It will feel like you hit a brick wall and the car will lose all power. The car will take longer and longer to start and will have hesitations at idle and cruise. If the car has been off for 6-8 hours, then you can check the fuel pressure in the morning by just applying power to the car, but not starting it. Power on the AP, put fuel pressure on the gauge screen, then turn the key to power on. In this situation the car has been off long enough and all the fuel has drained back into the tank, so when you power on the car and the LPFP primes to get fuel up to the engine the fuel pressure reading on the AP will be purely from the LPFP. It should go up to 52-55 psi, then slower taper down. If it only peaks at 30-40 psi and falls off quickly, that is concrete proof that the LPFP system is not sealed and therefore not holding pressure.
The LPFP should be installed w/ the white stock spacer and 2 o-rings. Even if it was installed correctly, it can still pop out of place over time and leak, or an o-ring can tear. This is an issue with both the DW300c and AEM340 fuel pumps. Neither fuel pump was specifically designed for the 15+ WRX so the fitment is not very good, which causes all these issues. The AEM pump fits ever so slightly worse because it is 1mm longer than the DW pump. The fitment is so tight on the pumps that it seems impossible for the fuel pump to move around and pop out of place, but it is actually fairly common.
2) Fuel Pressure Regulator O-Ring Leak
– basically the same exact issue described above, but on the fuel pressure regulator. The FPR is the silver thing
3) Your stock HPFP does not like e60-e70
– The stock HPFP’s on some cars simply don’t like the higher ethanol contents in the e60 – e70 range. These issues are due to the internals sticking from lack of lubrication. The pumps are lubricated by the fuel, so as the ethanol content is increased, the lubrication is decreased.
- This can easily be tested by adding pump gas and lowering the ethanol content down to e50-e55 and resetting the ECU to clear the CEL’s. If you need to drive and burn off some ethanol to make room for the pump gas, you can turn off the car and reset the will get rid of the CEL and make the car drive normally.
- If the fuel pressure drops go away when the ethanol content is lower, then it means that your stock HPFP simply can’t handle the higher ethanol. The tune will need to be adjusted to have the car make max power at e50. The car will still make the same exact power, the only difference will be that it occurs at e50 now instead of e60.
- If the fuel pressure continues to drop below 200 psi om e50, then #1 or #2 are the reason for the fuel pressure issues.
4) Fuel Pressure Sensor Connector/Wiring Issue
- The 0191, 0192 and 0193 CELs are for the pressure sensor itself and are usually thrown if one of its wires are cut or if it is simply not plugged in all the way.
Occasionally these fuel pressure CELs may also be thrown if you were simply low on gas and gulped up air bubbles in the gas tank.
Camshaft / Crankshaft CEL Causes
Subaru's Cam/Crank CEL Troubleshooting Order
These CELs are thrown when the low pressure fuel pump has been installed incorrectly. The fuel pump is leaking internally back into the fuel basket and starts working harder and drawing more current which can cause these CELs to be thrown. In some cases the fuel pump fuse will blow or the wiring can also melt. The CELs can also be thrown if the fuel pump connection on top of the basket has not been plugged in all the way.
99% of the time these CELs are from people not plugging the sensors in all the way after cleaning the MAF and MAP sensors. Unplug the sensor, re-plug it in, reset the ECU with the AP and the codes should be gone.
If the CELs persist after unplugging/re-plugging the sensors, then check the MAF extension cable for moisture and corrosion.
p0103 MAF Sensor Circuit High Input
CAI’s aren’t fully sealed like the stock intake and are more prone to having rain water get into the intake and onto the MAF sensor. Water on the MAF sensor will usually result in a rich condition and can make the car undrivable depending on the severity of the rain and water reaching the MAF sensor. This will usually throw a p0103 MAF Sensor Circuit High Input CEL. If you get this CEL and it’s raining and/or you just washed your car or went through a car wash, then you simply need to take the MAF out and blow it off with an air hose or spray it off with MAF cleaner, let it dry, re-install it, then reset the ECU under troubleshooting.
These CELs are thrown for leaks in the EVAP system. Most likely causes are the gas cap not being screwed on all the way or an EVAP hose popping off. The EVAP hoses are underneath the intake manifold on the passenger side.
A random combination of CEL's like this is almost always from a wiring harness connector not being plugged in all the way. Especially when they are all "circuit low" and "circuit high" CELs. This combination in particular was the brown plug underneath the intercooler.
Common Causes of p0606, b1572 and u0073
- The p0606 CEL is covered in TSB 07-75-13R.
- Anything that causes a power on/off in a short time frame.
- Disconnecting/reconnecting the battery.
- Aftermarket battery with loose battery terminal connections.
- Head-unit, speaker, amp install (from battery disconnect/reconnect)
- Headlight install (from battery disconnect/reconnect)
- Replacing the ECU (from battery disconnect/reconnect)
- Hesitating while turning the key when starting the car. IE, power on power off power on.
- Resetting the ECU.
- Flashing a tune.
Fixes
- I've never had a customer persistently throw this code and actually have an "internal control module processor" issue. The CEL has always cleared and never come back.
- Reset ECU to clear code. Carry on normally. Report if CEL returns.
Subaru Procedure from TSB 07-75-13R
- Reset ECU to clear RAM (memory).
- Turn the ignition ON then OFF normally one time. Wait for more than one minute before turning the ignition back ON again.
- This procedure allows the self-shutoff relay to power down, completing the self-shutoff procedure.
Usually from the sensor not being plugged in all the way or possibly a wire cut to the sensor. Contact your shop/tuner with the specific code.
Usually from the sensor not being plugged in all the way or possibly a wire cut to the sensor. Contact your shop/tuner with the specific code.
MY THEORY ON FAILING FLEX FUEL KITS
IS MY CAR SAFE TO DRIVE WHILE THROW COBB1/COBB2 CEL's? - short answer, no
The ethanol sensor controls the whole tune. If it's not reading the ethanol content correctly, the car won't run correctly. If you're on e60 and the CEL comes on, it changes the ethanol content to 10%.....which will make the car run like crap. But if you're on pump gas it would mostly be fine, but you would be in limp mode. But the cars usually run like crap in limp mode as the ecu is trying to make it run rich and pull timing because it thinks something is wrong. If you absolutely need to drive your car, my suggestion is to get on pump gas so the ethanol content will match the ethanol content if the CEL comes on. You can clear the CEL in the meantime while you go through the troubleshooting steps below with Cobb.
Cobb’s flex fuel troubleshooting guide is at the link. If you’re getting Cobb1 or Cobb2 CEL’s it means the voltage for the ethanol sensor is going out of range. THIS IS NOT A TUNING ISSUE. You will have to email Cobb. Cobb will ask you for a log to show the voltage out of range. Then they will tell you that there is possibly moisture or debris in the gas from the gas station and ask you to take the ethanol sensor out and blow it out with a compressor and reinstall it. They will ask you to log various parameters and catch it so they can review the data. Then they will say there is a possibility that it is a tuning issue and ask what your tuner has the voltage, sampling and delays set to. These are the settings that are in your map:
The ethanol sensor is a 0.5 to 4.5 volt sensor. Anything in that range is fine. CELs will only come on if the voltage is below 0.25 volts or above 4.75 volts for an extended period of time. That would mean the ethanol content is either pegged at 0% or 100%. You can watch/log ethanol raw and Sns Volts TGV L on the AP. those are what Cobb will want to see. So if you're getting the low voltage CEL the ethanol raw should be 0 and the voltage below 0.5 volts. Once you capture it in a log they will likely send you a new sensor under warranty.
There are specific voltages (+/- 0.03 V) the module outputs in specific scenarios. Some early kits did output 0.1 V for sensor fault when there really was just water in the fuel, but newer kits are more likely to provide more specific information to work from as you help a mechanic or customer diagnose flex fuel DTCs. The low and high voltages we've suggested as DTC thresholds provide plenty of buffer to the 0.5-4.5 V normal operating range, while allowing a DTC to be thrown in the following error states:
- Generally these CELs mean that the sensor simply isn't plugged in all the way or a wire leading to that sensor has been cut.
- Throwing multiple circuit CELs at the same time usually means that a battery post connector is loose and all the sensors are losing power or the battery is dying in general. Think of your car just as it was when it came from the factory. If the car is running fine for 6 months, then one day it starts throwing check engine lights or running funny, you would make an appointment at Subaru and have them check for a mechanical issue….you don’t take the car to Subaru and ask them to re-tune it for you. Issues that arise over time are rarely ever tuning issues. Tunes don’t go bad over time. 99.9% of the time it’s a mechanical issue that has become prevalent over time such as sensors or filters getting dirty. Keep this in mind when asking me to look at logs post tune. I do charge for troubleshooting. I simply can’t answer emails and look over logs for thousands of people for free all day long.
- Generally these CELs mean that the sensor simply isn't plugged in all the way or a wire leading to that sensor has been cut.
- Throwing multiple circuit CELs at the same time usually means that a battery post connector is loose and all the sensors are losing power or the battery is dying in general.
- Battery is beginning to die
- Corrosion on the MAF and/or MAF extension cable
- Over oiled intake filter
- Spark plugs
- Vacuum/Boost Leak (intercooler couplers, charge pipe, leaky bov)
Go to the broken window and get it all the way up or all the way down then hold the button in that same direction for 10-15 seconds. #magic
This warning usually appears when Cobb updates the software. IE, when trying to load a new Gen2 speed density map when a Gen1 map is installed. Since Gen2 doesn't match Gen1, the warning appears. Just click ok. Once the map is on the AP, click on it and look at the info at the bottom of AP Manager and verify the AP serial number and car year both match your vehicle. If they do, then proceed to flash the map and do the logging. If they don’t match, then email me back and let me know there is a discrepancy.
- The FA is greatly affected by temps over 90 degrees. At this temperature timing and boost are reduced in order to help prevent knock in the hot temperatures. The car will continue to lose power and feel sluggish as the temps go past 120, 130, etc. This is all based on the temp measured at the MAF sensor, NOT the ambient temp outside.
- The engine bay is scorching after sitting at a stop light, so it will feel very sluggish leaving a light in hot temps but will get back to normal as the airflow cools everything off.
- Temp and elevation changes are accounted for in the tune and should not really cause any issues.
· Intake air leak
· Faulty spark plug
· Fuel injector harness is open or shorted
· Fuel injector circuit poor electrical connection
· Ignition coil harness is open or shorted
· Ignition coil circuit poor electrical connection
· Insufficient cylinder compression
· Clogged or faulty fuel injector
· Faulty ignition coil
· Incorrect fuel pressure
- Only use OEM NGK Plugs
- Only purchase from from a Subaru specialty shop like Import Image Racing or New Provisions Racing or directly from Subaru
- Plugs cost around $45 from IIR or New Provisions Racing and they are ~$100 from Subaru
- The issue with purchasing plugs from a large wherehouse distributor like Amazon is that many of them will place products with the same part number on the same shelf no matter where they were source from. So even if you have a known reliable store on Amazon, it is still possible to receive fake plugs because they are on the same shelf in the wherehouse.
- Do NOT buy plugs from Amazon, eBay or any other wherehouse websites.
- Do NOT buy the BRZ “1 step colder” plugs from SMY. They are naturally aspirated plugs, they have the wrong gap for a WRX and will cause power loss and misfires in a WRX.
- Do NOT buy the Denso plugs. Stick to NGK.
- Do NOT Use anti-seize on the spark plug threads. NGK plugs are already coated and do not need anti-seize. It will mess up the torque readings.
- NGK Spark Plug Info - https://ngksparkplugs.com/en/resources/5-things-you-should-know-about-spark-plugs
- The plugs should come pre-gapped to 0.020 – 0.022, but you need to verify the gap before installation. - Torque spark plugs to 12.9 ft*lbs
- Torque coil packs to 6.3 ft*lbs
- Change every 20k miles
There are 4-6 different ways to be able to tell them apart. Just type in "Real vs Fake NGK" into YouTube and several videos will come up going over all the differences in detail. I am only going to mention one of them that seems like the easiest/quickest one to use to determine if yours are real.
The diagonal slashes right above the threads are very different between the reals and fakes.
DIAGONAL SLASHES (5) - there should be 5 diagonal slashes on the right side of the JAPAN engraving.
The slashes are short and have a 3D look and texture.
DIAGONAL SLASHES (4) - the fake ones only have 4 diagonal slashes on the right side of the JAPAN engraving. The slashes are longer, thinner and don't have the same 3D look and texture
The turbocharger air intake duct on affected vehicles may have been produced with incorrect material that is susceptible to cracking. Should the turbocharger air intake duct crack, the engine may develop an abnormally rough idle, lower power and possibly stall. Should the engine suddenly lose power or stall while driving, there is an increased risk of a crash. In addition, this condition may cause the “Check Engine” light located on the instrument panel to illuminate, indicating a malfunction has occurred. It could also have an adverse effect on vehicle exhaust emissions.