Check Engine Light ON with DTC P2096 – 2016 Mazda CX-5. P2096 mazda 3

P2096 Code Post Catalyst Fuel Trim System Too Lean Bank 1

OBD-II Trouble Code Technical Description

Article byDon BowmanASE Certified Automotive Tech

Post Catalyst Fuel Trim System Too Lean Bank 1

What does that mean?

This is a generic powertrain code, which means it covers all makes/models, 1996-newer. However, specific troubleshooting steps will vary depending on the vehicle.

The code P2096, post catalyst fuel trim system too lean on bank 1 simply translates to a lean (too much air and not enough fuel) condition the PCM recognized through the signals from the oxygen sensors. Bank 1 has no meaning on a four or straight six cylinder engine with a single exhaust. On a V-6 or V-8 engine it refers to the oxygen sensor on the number one cylinder side of the engine as bank 1.

A series of oxygen sensors in the exhaust system signal the fuel mixture ratio at all times. Each exhaust system with a catalytic converter will have two sensors -- one between the engine and the converter and one after the converter.

Oxygen sensors signal the engine management computer the amount of oxygen present in the exhaust, which is used in determining and controlling the fuel ratio. The higher the oxygen content the leaner the fuel mixture, conversely the opposite is a rich mixture. It does so in a series of pulses called "cross counts." There is zirconium on the tip of the sensor that reacts to oxygen in a way that when hot, creates its own voltage. It must be around 250 degrees F to operate and will produce up to 0.8 volts.

In operation the oxygen sensor will cycle once every second and send a voltage to the computer that ranges from 0.2 rich to 0.8 for a rich mixture. The perfect mixture will average the signals around 0.45 volts. The computer's target fuel/air ratio is 14.7:1. An oxygen sensor will not function at low temperatures such as start up -- for this reason most forward sensors have a pre-heater to reduce their warm up time.

The mission of the oxygen sensors are twofold -- to indicate the unburned oxygen in the exhaust and secondly, to indicate the proficiency of the catalytic converter. The engine-side sensor signals the mixture entering the converter and the rear sensor signals the mixture exiting the converter.

When the sensors and converter are operating properly, the front sensor will have a higher count than the rear sensor indicating a functioning converter. When the front and rear sensor agree, the front oxygen sensor has failed, the converter is plugged or another component is causing the oxygen sensor to give an erroneous signal.

This code may and may not be noticeable less for the check engine light. It depends on the cause, however, there isn't anything that can fail on a vehicle without adversely effecting something else. Trace the problem to correct the code as soon as possible to avoid damage to any other components.


The symptoms of a P2096 code will vary depending on the component or system causing the disruption in the fuel trim. Not all will be present simultaneously.

  • Malfunction Indicator Lamp (MIL) illumination with P2096 DTC set
  • Rough idle
  • Poor fuel economy
  • Poor acceleration
  • Misfire
  • Cherry red hot catalytic converter
  • Possible spark knock (detonation / pre-ignition)
  • Additional codes associated with the P2096

Potential Causes

The causes for this DTC may include:

  • Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors.
  • Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0304 for number 4.
  • A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly lean mixture.
  • A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
  • A plugged converter will cause of host of driveability problems as well as set this code. A severely plugged converter will result in the inability to increase rpm when under load. Look for a code such as P0420 -- catalytic converter efficiency below threshold if the converter indicating a faulty converter.
  • A faulty oxygen sensor. This will set a code in itself, however, a faulty oxygen sensor does not automatically condemn the sensor. The code just means that the sensor signal was not within specifications. An air leak or any of the above will cause an erroneous signal. There is a multitude of O2 codes relating to O2 performance which gives a clue to the problematic area.
  • The Mass Airflow sensor will also cause this problem. It would be accompanied by a code such as P0100 -- Mass Airflow circuit malfunction. The Mass Airflow sensor is a hot wire that senses the volume of air entering the intake manifold. The computer uses this information to control fuel mixture.
  • Rusty exhaust systems, cracked exhaust manifolds or damaged or missing gaskets or donuts will cause air leaks.

To make a point as to the cause and effect on vehicles, consider this scenario. A simple air leak forward of the number one oxygen sensor will add additional air to the mixture un-metered by the computer. The oxygen sensor signals a lean mixture due to the un-metered air.

Immediately the computer enriches the mixture to prevent a lean mixture from causing damage due to detonation among other factors. The unnecessarily rich mixture begins to foul the plugs, contaminate the oil, heats up the converter and drops the fuel economy. These are only a few of the things that transpire under these circumstances.

Diagnostic and Repair Procedures

It's wise to go online and acquire the technical service bulletins (TSBs) associated with these codes and a description. Although all vehicles suffer from similar causes, some may have a service history of problems with a particular component associated with this code.

If you have access to an advanced diagnostic scan tool such as a Tech II or Snap-On Vantage, this will save you a lot of time. The scanner has the ability to graph and display digital information in real-time of each sensor's performance. It will show the oxygen sensors in operation to easily recognize one that is malfunctioning.

Jeeps and some Chrysler products seem to suffer from poor electrical connectors, so inspect them thoroughly. Additionally, Jeeps have had several PCM updates on the later models. The reprogramming of the updates as well as oxygen sensor replacement for any reason is covered under the 8 year / 80,000 mile warranty. To check if the update has been completed, look next or behind the battery and there will be a serial number with the date of updating the computer. If it hasn't been done it is free for the above period.

  • Connect the code scanner to the OBD port under the dash. Turn the key to "On" with the engine off. Depress the "Read" button and the codes display. Cross-reference any additional codes with the accompanying code sheet. Direct your attention to these codes first.
  • In lieu of additional codes corresponding to code P2096 or P2098 test drive the vehicle and look for tell-tale symptoms. Fuel contamination will cause this code. Fill up with a higher grade.
  • If the vehicle displays very little power and difficulty in accelerating, look underneath the vehicle with the engine running. A clogged converter will normally glow red.
  • Check the engine for vacuum leaks between the Mass Airflow sensor and the intake manifold. Many times leaks sound like a whistle. Repair any leaks and clear the code.
  • If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition.
  • Look at the plug wires to make sure they are not burnt or laying on the exhaust.
  • Inspect the exhaust system. Look for rust holes, missing gaskets, cracks or looseness. Raise the vehicle and with a 7/8 inch wrench, make sure the oxygen sensor is tight. Inspect the wiring harness and connector.
  • If a code for the Mass Airflow sensor displays check its connector. If it is alright replace the MAF sensor.
  • Replace the oxygen sensor downstream the catalytic converter on the side of the engine with the number -1 cylinder for code P2096. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed.

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SOLVED: Fault code P2096 - Fixya

2005-2008 1- Turn Ignition switch to OFF & Run/Stop switch is to Run. 2- Push odometer reset button in & hold. 3- Turn ignition switch to Ignition and release odometer reset button. Background lighting sould illuminate, speedometer needle should sweep its full range and indicator lamps (battery, security, low fuel, check engine and cruise) should illuminate. The word "diag" should then appear. 4 - Push the odometer reset button once and you will see the selection menu "PSSPt" with the first P flashing. 5 - Each letter represents an area of the diagnostics module. The module that is flashing is the one you are going to check. To move from one letter (module) to the next, you push the odometer reset button one time. (from P to S to SP to t and back to P, etc.) P = ECM/ICM (Electronic Control Module [EFI] / Ignition Control Module [Carbureted]) S = TSM/TSSM (Turn Signal/ Turn Signal Security Module) SP = speedometer T = tachometer 6 - To get the DTC within an area of diagnostics, push and hold the odometer reset button in for 5 seconds and release. If there are any DTC's the code will be displayed or the word "none" will appear if there are no DTC's. Push the odometer reset button again to view additional codes if they exist. 7 - Record the codes. 8 - If DTC's are not to be cleared, Press and release the odometer reset button. Part number of module will be displayed. NOTE: To determine if a code is current or historic, clear the displayed code by pushing in and holding the odometer reset button ( longer than 5 seconds) until 'clear' comes up. Release the odometer reset button. Turn OFF the ignition switch. Run your bike and shut it down then recheck the DTC's again by repeating steps 1 to 9. If the code is current it will reappear. 9 - Press and release the odometer reset button to continue to the next module. 10 - Turn Ignition switch to OFF. On models not equipped with a tachometer "No Rsp" will appear when the tachometer identifier is selected. "No Rsp" will also appear if the run/off switch is in the off position when doing this procedure. HFSM = Hands Free Security Module TSM = Turn signal module Priority/DTC/Fault condition 1. P0605 ECM FLASH Memory Error 2. P0603 ECM EEPROM Memory Error 3. U1300 ECM Serial Data Low 4. U1301 ECM Serial Data High 5. U1097 Loss of Speedometer Serial Data to ECM 6. U1064 Loss of TSM/FSFM Serial Data to ECM 7. P1003 System relay contacts open 8. P1002 System Relay Coil High/Shorted 9. P1001 System Relay Coil Open/Low 10. P1004 System Relay Contacts Closed 11. P1009 Incorrect Password 12. P1010 Missing Password 13. P06415 V+Vref 1 Out Of Range 14. P06515 V+Vref 2 Out Of Range 15. P0373 CKP Sensor Intermittent 16. P0107 Map Sensor Open/Low 17. P0108 Map Sensor High 18. P0374 CKP Sensor Synch Error 19. P1600 EFI Module Processor Internal Error 20. P1270 TGS Validation Error 21. P2107 EFI Module Processor Internal Fault 22. P2122 TGS1 Low/Open 23. P2123 TGS1 High 24. P2127 TGS2 Low/Open 25. P2128 TGS2 High 26. P2138 TGS Correlation Error (Twist grip sensor) 27. P0120 TPS1 Range Error 28. P0220 TPS2 Range Error 29. P0122 TPS1 Low 30. P0123 TPS2 High/Open 31. P0222 TPS2 Low 32. P0223 TPS2 High/Open 33. P2135 TPS Correlation Error 34. P2119 EFI Motor Throttle Body Range Performance 35. P2100 EFI Motor Circuit Open 36. P2101 EFI Motor Circuit Range Performance (Actuation Error) 37. P2102 EFI Motor Circuit Low 38. P2103 EFI Motor Circuit High 39. P2176 EFI Closed Position Not Learned 40. P1514 Air Flow Fault 41. P2105 EFI Forced engine shutdown 42. P1501 Jiffy Stand Sensor Low 43. P1502 Jiffy Stand Sensor High 44. P0572 Brake Switch Low 45. P0117 ET Sensor Low 46. P0118 ET Sensor High 47. P0112I AT Voltage Low 48. P0113I AT Voltage Open/High 49. P1351 Front Ignition Coil Driver Open/Low 50. P1354 Rear Ignition Coil Driver Open/Low 51. P1352 Front Ignition Coil Driver High/Shorted 52. P1355 Rear Ignition Coil Driver High/Shorted 53. P1357 Front Cylinder Combustion Intermittent 54. P1358 Rear Cylinder Combustion Intermittent 55. P0261 Front Injector Open/Low 56. P0263 Rear Injector Open/Low 57. P0262 Front Injector High 58. P0264 Rear Injector High 59. P0562 Battery Voltage Low 60. P0563 Battery Voltage High 61. P0501 VSS Sensor Low 62. P0502 VSS Sensor High/Open.. 63. P1356 Rear Cylinder No Combustion 64. P1353 Front Cylnder No Combustion 65. P0444 Purge Solenoid Open/Low 66. P0445 Purge Solenoid High 67. P1475 Exhaust Actuation Position Error 68. P1477 Exhaust Actuator Open/Low 69. P1478 Exhaust Actuator Shorted/High 70. P0131 Front Oxygen Sensor Low 71. P0151 Rear Oxygen Sensor Low 72. P0132 Front Oxygen Sensor High 73. P0152 Rear Oxygen Sensor High 74. P0134 Front Oxygen Sensor Inactive 75. P0154 Rear Oxygen Sensor Inactive 76. P1510 EFI Limited Performance Mode 77. P1511 EFI Power Management Mode 78. P1512 EFI Forced Idle Mode 79. P0577 Cruise Control Input High


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Check Engine Light ON with DTC P2096 – 2016 Mazda CX-5 |



2016 CX-5 (SKYACTIV 2.5L A/T) vehicles with VINs lower than JM3KE******759448 (produced before December 24, 2015)


Check Engine Light ON with DTC P2096:00. No other engine air/fuel related DTC are stored.


This may be caused by improper PCM control logic.

NOTE: If other engine air/fuel related DTC are stored, this Service Information is not applicable. Refer to MS3 online for diagnosis and repair.

P2096:00 – H02S fuel injection control system – Air fuel too lean

The PCM control logic has been modified to eliminate this concern.



  1. Using IDS or Mazda J2534 99.01 or later software, reprogram the PCM to the latest calibration (refer to “Calibration Information” table) by following the “Module Reprogramming” procedure.


  • Always update the IDS tool first, then follow on-screen instructions to download the needed calibration file for PCM reprogramming.
  • It is not necessary to remove any fuses or relays during PCM reprogramming when the IDS screen prompts you to do so. You may accidentally stop power to one of the PCM terminals and cause the PCM to be blanked, or you may receive error messages during the IDS reprogramming procedure.
  • IDS shows the calibration part numbers after programming the PCM.
  • Please be aware that PCM calibration part numbers and file names listed in any Service Bulletin may change due to future releases of IDS software, and additional revisions made to those calibrations for service related concerns.
  • When reprogramming a PCM, IDS will always display the “latest” calibration P/N available for that vehicle. If any calibration has been revised/updated to contain new information for a new service concern/issue, it will also contain all previously released calibrations.
  • Start/Stop button vehicles only: DO NOT press the start/stop button during the reprogramming process.
  • When performing this procedure, we recommend using the “Power Supply” mode in the Battery Management System to keep the vehicle battery up to capacity. If a different charger is used, make sure it does not exceed 20 AMPS. If it exceeds 20 AMPS, it could damage the VCM.
  1. After performing the PCM reprogramming procedure, clear DTCs.
  2. After clearing DTCs, start the engine and confirm that no warning lights stay on.


  • If any DTCs should remain after performing DTC erase, diagnose the DTCs using MS3 online instructions or Workshop Manual section 01-02.
  • Disconnect the negative battery cable and wait for 30 seconds or more to reset the fuel control learning data.



Engine Transmission Drive File Name Memo
Calif A/T 2WD PYAJ-188K2-D Mitsubishi
PYAR-188K2-D Denso
4WD PYAK-188K2-C Mitsubishi
PYAS-188K2-C Denso
Fed 2WD PYAL-188K2-C Mitsubishi
PYAT-188K2-C Denso
4WD PYAM-188K2-D Mitsubishi
PYAV-188K2-D Denso



Approved J2534 Device with Mazda J2534 Software FMP & MMP

Mazda uses a very similar program to FMP, named MMP, MMP allows for reprogramming of PCMs only, no body modules.

The security information is separate from the programming subscription and you must email information to Mazda for the Immobilizer/PATS codes.

Some reflashes require access to TSBs, and they are not included in the programming subscription.

The MMP software covers model year 1996 and newer models for reprogramming.

All 1996 models and up can be reflashed except for Miata. Miata (MX-5) could be reflashed starting in 2006.

  • The application will determine whether or not a new calibration file is available.
  • If you choose to use the new file, the module will be reprogrammed.
  • If PATS functionality is required, it can be chosen from the toolbox.

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