P006B
MAP - Exhaust Pressure CorrelationP006B is a generic OBD-II powertrain diagnostic trouble code: MAP - Exhaust Pressure Correlation. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P006B means
Code P006B is stored when the Powertrain Control Module (PCM) detects that the voltage signals from the Manifold Absolute Pressure (MAP) sensor and the Exhaust Pressure Sensor (EPS) differ by more than a programmed threshold over a defined monitoring period. This code applies almost exclusively to diesel-powered vehicles, as petrol engines rarely use a dedicated exhaust back-pressure sensor. On diesel engines equipped with a diesel particulate filter (DPF) or exhaust gas recirculation (EGR) system, the ECU relies on the exhaust pressure sensor to manage regeneration cycles, EGR flow, and turbocharger vane positioning. The MAP sensor simultaneously monitors intake manifold pressure. Both sensors must produce readings that are physically consistent with each other for the PCM to confirm correct operation of the air-management system. When the two values diverge beyond tolerance — for example because the exhaust sensor has drifted, a wiring fault distorts one signal, or an exhaust restriction creates an abnormal pressure differential — the PCM logs P006B and illuminates the MIL. Ignoring this fault risks uncontrolled EGR flow, failed DPF regeneration, or incorrect turbo vane actuation, all of which can cause excessive black smoke, increased fuel consumption, and accelerated engine wear.
Common causes
Most-frequently reported root causes when P006B is logged.
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1
Defective exhaust pressure sensor producing a drifted or fixed voltage output
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2
Faulty MAP sensor with degraded or erratic pressure response
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3
Open circuit, short circuit, or corroded wiring and connector pins in the exhaust pressure or MAP sensor circuits
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4
Blocked or soot-clogged exhaust pressure sensor impulse pipe causing a false low-pressure reading
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5
DPF or EGR system restriction creating an abnormally elevated exhaust back-pressure that the MAP sensor cannot correlate with
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6
Vacuum or boost leak on the intake side shifting MAP readings away from expected values
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7
PCM software error or corrupted calibration data
Symptoms drivers notice
How to diagnose P006B
A typical diagnostic flow when this code is present.
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1
Connect an OBD-II scanner, retrieve all stored codes and freeze frame data; note any accompanying DPF, EGR, or turbocharger codes that may share a root cause
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2
Visually inspect the exhaust pressure sensor impulse pipe for blockage with soot or carbon deposits — disconnect and blow through it to confirm it is clear
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3
Inspect all wiring and connectors at both the MAP sensor and exhaust pressure sensor for corrosion, chafing against hot exhaust components, or loose terminals
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4
With the engine running, compare live MAP and exhaust pressure sensor readings on the scanner to identify which value is out of expected range for the operating conditions
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5
Apply known vacuum or pressure to each sensor using a hand pump and verify the sensor output voltage tracks correctly across the range; replace any sensor that does not respond linearly
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6
Test 5 V reference supply and ground continuity at each sensor connector with a digital multimeter; repair any open or high-resistance circuits found
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7
Clear codes and perform a test drive including a period of sustained load; if P006B returns promptly, proceed to PCM connector pin-level circuit testing before considering PCM replacement
Related powertrain codes
Frequently asked questions
Is P006B a diesel-only code?
In practice, yes. Dedicated exhaust pressure sensors are standard on diesel engines equipped with a DPF or variable-geometry turbocharger. Petrol engines very rarely use an exhaust pressure sensor, so P006B is almost always encountered on diesel-powered vehicles.
Can a clogged impulse pipe cause P006B without any actual sensor failure?
Yes, this is a very common cause. The small-diameter pipe connecting the exhaust pressure sensor to the exhaust manifold can become blocked with carbon soot, causing the sensor to read atmospheric pressure rather than actual exhaust pressure. Cleaning or replacing the impulse pipe often resolves the fault without any sensor replacement.
Will P006B cause DPF regeneration to fail?
Yes. The PCM uses the exhaust pressure differential across the DPF to determine when regeneration is needed. A false or absent exhaust pressure signal means the PCM cannot accurately assess DPF soot loading, which may prevent active regeneration and eventually lead to DPF blockage.
Can I drive normally with P006B active?
Short distances at reduced load are generally tolerable, but extended driving is not advisable. If the PCM enters limp mode or EGR/DPF management is impaired, engine damage from over-fuelling or DPF blockage can follow. Diagnosis and repair should be prioritised promptly.
Disabling P006B in software
RaceTune can permanently disable P006B — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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