THE CODE DIRECTORY

Diagnostic code references — Page 75.

Browse canonical reference entries. Each definition keeps its own source and vehicle-applicability limits.

Generic OBD-II

P21EC

These are code references, not a list of confirmed faults on every vehicle. Read the source and applicability notes, then match the exact vehicle, year, engine and scan report.

Cylinder 9 Injector B Circuit Low

Cylinder 9 Injector B Circuit High

Cylinder 10 Injector B Circuit Low

Cylinder 10 Injector B Circuit High

Cylinder 11 Injector B Circuit Low

Cylinder 11 Injector B Circuit High

Cylinder 12 Injector B Circuit Low

Cylinder 12 Injector B Circuit High

Fuel Control System B Too Lean Off Idle Bank 1

Fuel Control System B Too Rich Off Idle Bank 1

Fuel Control System B Too Lean Off Idle Bank 2

Fuel Control System B Too Rich Off Idle Bank 2

Why bank 1’s lean idle code depends on the port-injection adaptation

Understanding a rich idle adaptation on bank 1’s PFI fuel path

Bank 2’s lean idle adaptation on the port-injection fuel path

A rich idle correction on bank 2’s port-fuel-injection path

Fuel Control System B Too Lean at Higher Load Bank 1

Fuel Control System B Too Rich at Higher Load Bank 1

Fuel Control System B Too Lean at Higher Load Bank 2

Fuel Control System B Too Rich at Higher Load Bank 2

An upstream NOx circuit code includes controller self-check failures

NOx sensor 1 internal current-control stability

NOx sensor 1 reports below its usable concentration range

engine-out NOx raw value exceeds the sensor range

NOx signal validity requires supply and communication checks

NOx sensor 1 heater-control open-circuit diagnosis

NOx heater-control short to ground after dewpoint

NOx sensor 1 heater circuit short toward power

NOx heater-sense open circuit is separate from heater control

NOx heater resistance deviates from its target after several delays

NOx sensor 1 supply falls low while relay voltage remains adequate

post-catalyst NOx sensor supply-voltage supervision

NOx Sensor Supply Voltage Circuit Bank 2 Sensor 1

NOx Sensor Supply Voltage Circuit Bank 2 Sensor 2

Upstream NOx heater performance has electrical and control branches

Tailpipe NOx heater sensing can fail even when some heating occurs

NOx heater-sense connection is shorted to ground

NOx heater-sense circuit has a short-to-power indication

NOx Sensor Heater Sense Circuit Intermittent Bank 1 Sensor 1

NOx Sensor Circuit Bank 2

NOx Sensor Circuit Range/Performance Bank 2

NOx Sensor Circuit Low Bank 2

NOx Sensor Circuit High Bank 2

NOx Sensor Circuit Intermittent Bank 2

NOx Sensor Heater Control Circuit/Open Bank 2

NOx Sensor Heater Control Circuit Low Bank 2

NOx Sensor 1/2 Correlation Bank 1

NOx Sensor 1/2 Correlation Bank 2

Why low DEF line-heater current must be judged with a positive command

reductant line-heater current exceeds its operating limit

Identifying inadequate current in the second DEF tank heater

second tank-heater channel draws excessive current

NOx Sensor Heater Control Circuit High Bank 2

NOx Sensor Heater Sense Circuit Bank 2

NOx Sensor Heater Sense Circuit Range/Performance Bank 2

NOx Sensor Heater Sense Circuit Low Bank 2

NOx Sensor Heater Sense Circuit High Bank 2

NOx Sensor Heater Sense Circuit Intermittent Bank 2

Internal barometric sensor communication or memory fault

three-sensor comparison isolates barometric-pressure disagreement

LIN-reported barometric pressure is below the permitted range

The LIN barometric-pressure value exceeds its upper limit

Barometric Pressure Sensor B Circuit

Separating physical pressure range faults from sensor cross-check failures

Why barometric sensor B circuit-low can be a digital count limit

Understanding a high digital reading from barometric sensor B

Barometric-pressure sensor B changes too erratically

Barometric Pressure Sensor A/B Correlation

Barometric pressure fluctuates too much over consecutive samples

heater influence is detected through upstream sensor current variation

Detecting heater interference in the bank 1 rear oxygen-sensor signal

O2 Sensor Signal Circuit Shorted to Heater Circuit Bank 1 Sensor 3

bank-two heater coupling is evaluated under controlled sensor conditions

A bank 2 rear oxygen-sensor fault linked to heater switching

O2 Sensor Signal Circuit Shorted to Heater Circuit Bank 2 Sensor 3

Wide-range oxygen sensor pump-current circuit is diagnosed open

the pump-circuit check uses missing lean response during fuel shutoff

pump-circuit diagnosis follows a qualified control-factor change

Reductant Heater E Control Circuit

Reductant Heater F Control Circuit