Fix P2BAC: Mechanic’s solutions that WORKED

The P2BAC: NOx Exceedance – Deactivation of EGR points out a fault in the vehicle’s emissions system, indicating an excess of NOx gases due to the deactivation of the EGR system. This is often accompanied by other exhaust system-related codes.

P2BAC quick overview

Meaning	P2BAC: NOx Exceedance – Deactivation of EGR
Is it serious?	This code indicates an emissions-related fault. It’s important for environmental compliance but is not typically an immediate threat to vehicle functionality.
Possible causes	– Damaged, burnt, or corroded wiring/connectors in EGR valve’s control circuit – Defective or clogged EGR valve – Clogged exhaust gas feed tube – Clogged EGR passages in the cylinder head – Defective PDFE sensor on certain applications
How to diagnose?	Check EGR Valve: Inspect the EGR valve for clogs or damage. Inspect Wiring/Connectors: Examine wiring and connectors for damage or corrosion. Evaluate Exhaust Feed Tube: Check the exhaust gas feed tube for blockages. Assess EGR Passages: Inspect the EGR passages in the cylinder head for clogging. Consider PDFE Sensor: On applicable models, check the PDFE sensor for issues. PCM Evaluation: Rarely, a failing PCM could be the cause; consider after ruling out other issues.

How to fix P2BAC – learn from mechanics

I looked into P2BAC service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Ram

Vehicle Information: 2011 Ram 3500 Laramie 6.7L

Issue + Repair History:

• Check engine light on after installing new rear tires.
• Cleared codes, but code P2BAC reoccurred after a short drive.
• No other powertrain codes present currently.
• No performance issues noticed during driving.

Other OBD2 Codes + Test Results:

• P246f: Exhaust gas temp 1/4 performance.
• P2563: Turbo position sensor.
• P2262: Turbo boost pressure not detected.
• P0299: Turbo underboost.
• P2BAC: NOX exceeded deactivation of EGR.

Suggestions to Fix Issue:

• Check and clean EGR valve and passages.
• Monitor exhaust temp sensors for potential issues.
• Look for any aftermarket chip installation and remove if present.
• Consider a possible reflash as per TSBs.
• Inspect for coked up turbo and consider cleaning method.
• Clean the EGR valve seat and check EGR cooler.

Final Fix:

• Found that the exhaust gas temp sensor code reoccurred.
• Discovered harness rubbed through likely by metal bracket contact.
• Replaced the assembly with an OEM part from the dealer.
• After a 50-mile test drive and a week of customer driving, no codes reappeared. Issue resolved.

Case #2: Ram

Vehicle Information: 2011 Ram 3500 Laramie 6.7L

Issue + Repair History:

• Truck experiencing hesitation, with MIL lamp on.
• Codes P2262 (Turbo Boost pressure not detected – Mechanical) and P2BAC (NOx exceeded, deactivation of EGR) present.
• Exhibiting sluggish performance despite showing boost on scanner.
• Previously had issues with regen, sensors in exhaust replaced.

Other OBD2 Codes + Test Results:

• Cleaned EGR.
• Replaced air filter and checked/cleaned turbo ducting.
• Replaced fuel filter.

Suggestions to Fix Issue:

• Check if turbo has a cleanout port; clean turbo using Mopar cleaning solution if available.
• Consider flashing ECM with latest software updates.
• Order special tool and solution to clean the turbo, may need a dealer tech to assist.
• Check turbo shaft end play with a dial indicator for potential turbo issues.

Final Fix:

• Replaced O2 sensor and performed the latest updates at the dealer.
• Dealer confirmed turbo was not sooted up.
• Rechecked all turbo ducting, air intake, and cooler.
• Changed all filters.
• Truck performance improved but not completely resolved; further investigation planned.

Case #3: Ram

Vehicle Information: 2016 Ram 3500 Big Horn 6.7L

Issue + Repair History:

• Check engine light on, low power on acceleration.
• Found code P0087 (low fuel rail pressure).
• Replaced transfer pump with OEM pump and both fuel filters, restoring normal volume at injection pump.
• Replaced turbo due to stuck waste gate.
• Despite repairs, P0087 code reappears consistently.
• Commanded fuel rail pressure is 24-25k, actual is 14-19k.
• Tried new Fuel Control Actuator (FCA) without success.
• Injection pump and rail plug are newer but without detailed records.

Other OBD2 Codes + Test Results:

• P0087: Fuel rail pressure low.
• P2BAC: NOx exceeded, deactivation of EGR.

Suggestions to Fix Issue:

• Check return flow, possibly excessive due to bad injector.
• Re-torque connecting tubes to 41 Ft. Lbs and retest.
• Perform injector return flow test.
• Check if relief valve is holding pressure or bypassing to the tank.
• Inspect tank for debris, particularly in the lift pump.
• Verify supply pump pressure and injector flow.
• Consider checking the fuel in the tank for crud or blockages.

Final Fix:

• Installed new injectors in the truck.
• Fuel rail pressure returned to normal, and truck was able to reach maximum pressure as usual.

Case #4: Ram

Vehicle Information: 2013 Ram 2500 SLT 6.7L, MIL Lamp on, low power

Issue + Repair History:

• New purchase, MIL comes on after 50 miles.
• Sets P2262 and EGR code.
• Experiences low power at full throttle.
• Fuel pressures are normal.
• Battery light comes on; PCM shows 14.6 charge command, but no charging.
• Plans to replace batteries.
• Considering PCM reflash for the P2262 code.
• Planning to use BG EPR and Diesel Care FI clean.
• Queries about running turbo clean with FI clean, and whether to run static Regen.
• Investigating how to test for actual plugged EGR or Exhaust.
• Dealer suggested extensive and expensive repairs.
• Warranty company declined coverage due to pre-existing condition.
• No history of previous repairs.

Other OBD2 Codes + Test Results:

• P2bac: NOx Exceeded, Deactivation of EGR
• P2262: Boost pressure A not detected
• EGR Temp 1: 900, EGR Temp 2: 1100, EGR Temp 3: 1000, EGR Temp 4: 1100

Suggestions to Fix Issue:

• Remove VGT actuator from the turbo and check for broken gear.
• Inspect turbo for free turning and replace VGT actuator if necessary.
• Consider aftermarket components potentially damaging the engine.
• Inspect fuel filter and get a fuel sample if replacing turbo.
• Check recalls for the vehicle.
• Clean turbo if VGT is good.
• Replace actuator if turbo vanes move freely without binding.
• Consider aftermarket turbo recommendations due to existing tuner.
• Note that the code P2262 cannot be overwritten by a programmer as it affects engine/turbo performance.

Final Fix:

• The turbo was found to be fine, but the actuator had issues.
• The problem was identified as either requiring a thorough cleaning or replacement of the actuator.
• Vehicle had BG 245 in the fuel; it set the code every few days.
• During testing, actual and desired VGT readings matched nearly perfectly.
• The final resolution involved addressing the actuator, with the possibility of a tear down and cleaning or replacement.

Case #5: Ram

Vehicle Information: 2014 Ram 2500 Laramie 6.7L, MIL Lamp on

Issue + Repair History:

• Customer experienced low power and low boost issues.
• Installed a pre-calibrated VGT from an online company.
• Triggered P0299 and P00AF codes.
• No leaks found in intercooler.
• Re-calibrated VGT actuator, but issue persisted.
• Truck performed well until the engine heated up, then triggered pending codes and stopped using the actuator.
• Rebuilt turbo as adjuster might get sticky when hot, but still received P00AF code.
• Replacement VGT module under warranty also gave P00AF code.
• No TSB or flash updates found for this issue.
• P2BAC code also appeared alongside P00AF.
• Rebuilt actuator replaced; discovered actuator motor was too weak to move the vanes.
• Finally resolved by replacing with a different actuator.

Other OBD2 Codes + Test Results:

• P0299: Boost performance
• P00AF: Boost control module performance
• Boost pressure: 25-30

Suggestions to Fix Issue:

• Check for a possibly plugged exhaust.
• Inspect exhaust psi tubes, EGR cooler, EGR piping manifold, or map sensor for carbon.
• Verify turbo VGT gear arm timing and internal carbon buildup.
• Check wiring connections to the turbo.
• Evaluate VGT position matching desired value, consider aftermarket tuning.
• Test exhaust brake function before and after the derate occurs.
• Use bi-directional control to stroke the VGT actuator both cold and hot, and compare commanded and actual positions.

Final Fix:

• The final fix involved replacing the rebuilt VGT actuator with a different one. The problem was due to the actuator motor being too weak to effectively move the vanes, particularly when hot. This solution resolved the issue, and no further problems were reported.

Diagnostic Step	Description
Inspect EGR System	Check EGR valve for any clogging or damage. Ensure proper wiring and connector condition.
Check EGR Passages	Look for any clogging in the EGR passages within the cylinder head.
Evaluate Exhaust Gas Feed Tube	Inspect the tube feeding exhaust gas to the EGR valve for blockages.
Assess PDFE Sensor	On certain applications like Ford, check the PDFE sensor for defects.
PCM Check	Rarely, a failing PCM could be the cause; rule out other issues before considering this.