2012 Altima S...replaced MAF sensor. Check engine light w...


2012 Altima S...replaced MAF sensor. Check engine light was off for about a week, but came back on last night...why? Mechanic's Assistant: Does the light stay on, or does it blink? Stays on Mechanic's Assistant: A...

2012 Altima S...replaced MAF sensor. Check engine light was off for about a week, but came back on last night...why? Mechanic's Assistant: Does the light stay on, or does it blink? Stays on Mechanic's Assistant: Are you fixing your Altima yourself? What have you tried so far? Myself....replaced the mass air flow sensor

Automotive Expert
Hi! My name is \*\*\*\*\* \*\*\*\*\* I will be able to assist you. I’m sorry that you’re having trouble with your vehicle. Don’t worry though, we’ll be able to figure this out. Please understand that I do not know your knowledge or capabilities so I may need to ask questions to find out basic information to help solve your specific problem. With most newer automobiles, they have sophisticated electrical systems that can rely on different computers or modules to keep everything operating correctly. Most of the time specialized equipment is needed to test these systems. If you do not have this type of equipment for testing then we can only guess what the problem is. Yes there are common failures for certain symptoms but without testing, there’s no way to determine the specific problem unless testing is done. Who do I have the pleasure of speaking with today? My goal is to give you the best service possible and to help you. If you have any questions or concerns, please don’t hesitate to let me know. Sometimes it may take a moment for me to respond because I may have to look up information about your concern. I appreciate your patience and will provide responses as soon as possible. The system will give you an automated phone call offer to speak to one of us on the phone **. It is optional.** Some folks prefer to talk on the phone. If you don’t, please ignore it as I cannot control the offer from popping up. My goal is to earn a 5 star rating experience. Any questions you have about this concern, please feel free to reply back to me. If I’m not online at the time, I will respond ASAP when I get back. The check engine light will come on when the computer sees a problem that affects the performance of the engine or transmission. There are many problems that can fail that will trigger this. It could be a faulty sensor, wiring issue, module fault, engine malfunction, etc. To see what specifically is causing the light to come on the vehicle will need to be tested with a scan tool that connects to the vehicle. This test will provide a trouble code that describes what specific system is having the problem. If you can have the vehicle scanned and can give me the code, I will be able to tell you specifically what is wrong with it. If you do not have a scan tool then you can bring your vehicle to any auto part store and they will scan it for free and give you the trouble code. I would do this ASAP so that we can determine what the problem is and keep any other problems from happening.

I had it scanned last week and the problem was the MAF sensor...so I replaced it. The light went off and stayed off for a week. And is now back on again. What would cause that?2012 Nissan Altima S
Automotive Expert
It could be anything. The check engine light will come on when the computer sees a problem that affects the performance of the engine or transmission. There are many problems that can fail that will trigger this. It could be a faulty sensor, wiring issue, module fault, engine malfunction, etc. To see what specifically is causing the light to come on the vehicle will need to be tested with a scan tool that connects to the vehicle. This test will provide a trouble code that describes what specific system is having the problem. If you can have the vehicle scanned and can give me the code, I will be able to tell you specifically what is wrong with it. If you do not have a scan tool then you can bring your vehicle to any auto part store and they will scan it for free and give you the trouble code. I would do this ASAP so that we can determine what the problem is and keep any other problems from happening.

i was told that i might need to have the ECU reprogramed because i replaced that sensor...is that true?
Automotive Expert
No that is not true. You'll need to scan it again and see what code is coming up.

i plan to...but that question was found on this website and a mechanic on here said that it did have to be reprogramed. Thats why i paid to ask about this...to find out for sure...but i am going to have it scanned to see if the code is the same...
Automotive Expert
Ok sounds good.

it came back with a P101 code...same as beforesorry, i meant P0101
Automotive Expert
I'm offline right now. I'll respond tomorrow.
Automotive Expert
Here's some testing you can do: DTC CONFIRMATION PROCEDURE 1. PRECONDITIONING If DTC CONFIRMATION PROCEDURE has been previously conducted, always perform the following procedure before conducting the next test. 1.Turn ignition switch OFF and wait at least 10 seconds. 2.Turn ignition switch ON. 3.Turn ignition switch OFF and wait at least 10 seconds. - GO TO 2. 2. PERFORM DTC CONFIRMATION PROCEDURE 1.Start engine and warm it up to normal operating temperature. 2.Drive the vehicle for at least 5 seconds under the following conditions: CAUTION: Always drive vehicle at safe speed. NOTE: - The gear must be fixed while driving the vehicle. - Keep the accelerator pedal as steady as possible during cruising. 3.Check 1st trip DTC. Is 1st trip DTC detected? YES- Proceed to "Diagnosis Procedure". NO- INSPECTION END Diagnosis Procedure 1. CHECK INTAKE SYSTEM Check the following for connection. - Air duct - Vacuum hoses - Intake air passage between air duct and intake manifold Is the inspection result normal? YES- GO TO 2. NO- Reconnect the parts. 2. CHECK GROUND CONNECTION 1.Turn ignition switch OFF. 2.Check ground connection E9. Refer to Ground Inspection in See: Vehicle \> Initial Inspection and Diagnostic Overview \> Circuit Inspection. Is the inspection result normal? YES- GO TO 3. NO- Repair or replace ground connection. 3. CHECK MAF SENSOR POWER SUPPLY CIRCUIT 1.Disconnect mass air flow (MAF) sensor harness connector. 2.Turn ignition switch ON. 3.Check the voltage between MAF sensor harness connector and ground. Is the inspection result normal? YES- GO TO 5. NO- GO TO 4. 4. DETECT MALFUNCTIONING PART Check the following. - Junction block connector E44 - Harness connector E11,F2 - 15A fuse (No.42) - Harness for open or short between mass air flow sensor and ECM - Harness for open or short between mass air flow sensor and IPDM E/R - Repair open circuit or short to ground or short to power in harness or connectors. 5. CHECK MAF SENSOR GROUND CIRCUIT FOR OPEN AND SHORT 1.Turn ignition switch OFF. 2.Disconnect ECM harness connector. 3.Check the continuity between MAF sensor harness connector and ECM harness connector. 4.Also check harness for short to ground and short to power. Is the inspection result normal? YES- GO TO 6. NO- Repair open circuit or short to ground or short to power in harness or connectors. 6. CHECK MAF SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT 1.Check the continuity between MAF sensor harness connector and ECM harness connector. 2.Also check harness for short to ground and short to power. Is the inspection result normal? YES- GO TO 7. NO- Repair open circuit or short to ground or short to power in harness or connectors. 7. CHECK INTAKE AIR TEMPERATURE SENSOR Check intake air temperature sensor. See: A L L Diagnostic Trouble Codes ( DTC ) \> P Code Charts \> IAT Sensor For USA And Canada. Is the inspection result normal? YES- GO TO 8. NO- Replace mass air flow sensor (with intake air temperature sensor). See: Air Cleaner Housing \> Removal and Replacement \> Removal And Installation. 8. CHECK EVAP CONTROL SYSTEM PRESSURE SENSOR See: A L L Diagnostic Trouble Codes ( DTC ) \> P Code Charts \> EVAP Control System Pressure Sensor For USA And Canada. Is the inspection result normal? YES- GO TO 9. NO- Replace EVAP control system pressure sensor. See: Evaporative Vapor Pressure Sensor \> Removal and Replacement \> Removal And Installation. 9. CHECK MASS AIR FLOW SENSOR Refer to "Component Inspection". Is the inspection result normal? YES- GO TO 10. NO- Replace mass air flow sensor. See: Air Cleaner Housing \> Removal and Replacement \> Removal And Installation. 10. CHECK INTERMITTENT INCIDENT See: Vehicle \> Initial Inspection and Diagnostic Overview \> Intermittent Incident. - INSPECTION END Component Inspection 1. CHECK MASS AIR FLOW SENSOR-I With CONSULT 1.Turn ignition switch OFF. 2.Reconnect all harness connectors disconnected. 3.Start engine and warm it up to normal operating temperature. 4.Connect CONSULT and select "DATA MONITOR" mode. 5.Select "MAS A/F SE-B1" and check indication. Without CONSULT 1.Turn ignition switch OFF. 2.Reconnect all harness connectors disconnected. 3.Start engine and warm it up to normal operating temperature. 4.Check the voltage between ECM harness connector and ground. Is the inspection result normal? YES- GO TO 4. NO- GO TO 2. 2. CHECK FOR THE CAUSE OF UNEVEN AIR FLOW THROUGH MASS AIR FLOW SENSOR 1.Turn ignition switch OFF. 2.Check for the cause of uneven air flow through mass air flow sensor. Refer to following. -Crushed air ducts -Malfunctioning seal of air cleaner element -Uneven dirt of air cleaner element -Improper specification of intake air system parts Is the inspection result normal? YES- GO TO 4. NO- GO TO 3. 3. CHECK MASS AIR FLOW SENSOR-II With CONSULT 1.Repair or replace malfunctioning part. 2.Start engine and warm it up to normal operating temperature. 3.Connect CONSULT and select "DATA MONITOR" mode. 4.Select "MAS A/F SE-B1" and check indication. Without CONSULT 1.Repair or replace malfunctioning part. 2.Start engine and warm it up to normal operating temperature. 3.Check the voltage between ECM harness connector and ground. Is the inspection result normal? YES- INSPECTION END NO- GO TO 4. 4. CHECK MASS AIR FLOW SENSOR-III With CONSULT 1.Turn ignition switch OFF. 2.Disconnect mass air flow sensor harness connector and reconnect it again. 3.Start engine and warm it up to normal operating temperature. 4.Connect CONSULT and select "DATA MONITOR" mode. 5.Select "MAS A/F SE-B1" and check indication. Without CONSULT 1.Turn ignition switch OFF. 2.Disconnect mass air flow sensor harness connector and reconnect it again. 3.Start engine and warm it up to normal operating temperature. 4.Check the voltage between ECM harness connector and ground. Is the inspection result normal? YES- INSPECTION END NO- Clean or replace mass air flow sensor.

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