|Trouble Code||Fault Location||Probable Cause|
|P00BD||Mass or Volume Air Flow "A" Circuit Range/Performance - Air Flow Too High||-|
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What Does Code P00BD Mean?
To properly meter the quantity of fuel for any given moment of engine operation, the engine control module (ECM) or powertrain control module (PCM) uses data from several sensor inputs. A few of the most critical are revolutions per minute (RPM), calculated from the crankshaft position sensor (CKP), intake air temperature (IAT), mass air flow (MAF), engine coolant temperature (ECT), and exhaust oxygen content, such as from air-fuel ratio sensors (AFR) or lambda sensors. During open loop (OL) operation, the ECM uses mainly CKP, MAF, and IAT to modulate injector pulse width (IPW) according to a pre-programmed map. Once the engine reaches closed loop (CL) operation, usually determined by a combination of runtime, ECT, and AFR readings, the ECM uses AFR to fine tune IPW.
Because oxygen content is proportional to air mass, this is a good way for the ECM to calculate IPW for best performance and emissions. At any given moment while the engine is operating, ECM programming expects to see MAF sensors readings, usually grams per second (g/s) within a specific range. Consider, for example, a 3.0-liter engine running at an unloaded 1,000 rpm. The ECM generally expects to see a MAF reading of 6 g/s, give or take a couple grams, depending on engine load. It might be half if the vehicle has two MAF sensors.
If the ECM sees MAF readings higher or lower than expected, typically 20 to 25 percent higher or lower, this is considered to be a fault. The ECM will store a diagnostic trouble code (DTC) and freeze frame data (FFD), illuminate the malfunction indicator light (MIL), and put the engine in OL or limp home mode (LHM). In this case, DTC P00BD is defined as Mass Air Flow (MAF) “A” Circuit Range/Performance – Air Flow Too High, that is, MAF air flow readings are higher than the expected range for a particular engine speed and load range.
Where is the P00BD sensor located?
The MAF sensor is mounted to the intake air tube, somewhere between the air filter and the throttle plate. It samples a portion of the air, sending a signal to the ECM to calculate the mass of air entering the intake. The MAF sensor is typically easy to find, though it may be under an engine cover. The MAF connector may have up to six wires if the IAT in integrated. On vehicles with dual throttle plates, there will be matching left and right MAF sensors.
What are the common causes of code P00BD?
Depending on year, make, and model, DTC P00BD may have number of causes. Here are some of the most common.
- Aftermarket Intake – Upgrading the intake tubing cane cause problems with MAF sensor readings. Any differences between the original equipment manufacturer (OEM) and aftermarket intake, such as internal diameter or surface finish, can skew MAF readings. In particular, if the new tubing is smaller, the sample will be higher than expected.
- Faulty IAT – In come Ford vehicles, MAF calculations include IAT readings. Many users have noted the discrepancy on particularly cold days.
- Faulty MAF – Internal partial short circuits could cause MAF readings to measure abnormally high.
- Blocked MAF Screen – On some vehicles, if the screen before the MAF sensor element is blocked or contaminated, this can skew air flow readings.
How expensive is it to fix code P00BD?
This is not a fault easily diagnosed if not addressed by a service bulletin (SB) or service campaign (SC). It will require a competent diagnostic technician and perhaps a couple hours of diagnosis. If the fault is electrical, additional repair time may be required. Sensor prices vary, and replacement times are usually low.
What are the symptoms of code P00BD?
- Poor Performance – When in OL or LHM, the engine may not perform as expected, limiting available power and maximum engine rpm. Additionally, an automatic transmission may be limited to reverse and only a couple of forward gears.
- Poor Fuel Economy – In OL mode, the ECM does not rely on AFR sensors to fine-tune fuel injection, defaulting to a richer air fuel ratio and increased fuel consumption.
What are common solutions to code P00BD?
There is usually no obvious solution for this problem for most vehicles.
- Some Ford vehicles did have an issue with the IAT sensor, which required a new IAT sensor and an ECM update.
How serious is code P00BD?
The vehicle should run well enough for you to drive it, though it may not run highway speeds. It is possible, though unlikely, the rich running conditions may overload the catalytic converter.
How safe is it to still drive the car with code P00BD?
Your vehicle should be safe enough to drive, but limited power and speed may make highway merging difficult, if not impossible. You may not be able to achieve minimum highway speed, which can be dangerous for you and other drivers.
How difficult is it to repair code P00BD?
First address loose electrical connectors and obvious sensor or electrical damage. Cleaning the MAF is not likely to solve the problem, as contaminated MAF sensors usually cause the opposite problem, insufficient air flow measurements. Partial blockage will be obvious, but you will need some basic hand tools to remove the intake tube for a complete visual inspection.
What are the common mistakes when repairing code P00BD?
Do not simply replace the MAF sensor because “it is a MAF code.” Unless there is obvious damage to the sensor, you will likely just waste your money and time. Similarly, do not replace the ECM because other fixes were not successful. If there is a MAF sensor fault, DTC P00BD may be accompanied by other MAF-related DTCs. Otherwise, more investigation is needed. Be sure to clear codes after any repairs and test drive to replicate the conditions indicated in the FFD.
How do you troubleshoot code P00BD?
Use an OBD2 scan tool to read DTC and FFD information. You’ll need a digital multimeter (DMM) to check the circuit wiring between the ECM and MAF. Electrical repairs may require soldering or pin removal tools.