Fuel Delivery

Tank to injector tip — lift pump, filter, high-pressure pump, rail, regulator and injectors. On direct-injection and diesel systems the pressures involved are extreme, which makes both the diagnostic care and the failure consequences greater than on older port-injected engines.

902 codes · 22 components · 15 live parameters

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Components

Live parameters to watch

PID	Parameter	Unit	Conversion
01:03	Fuel system status Whether fuelling is running open-loop or closed-loop, per bank. Open loop means the module is ignoring the oxygen sensors and using a fixed map — expected when cold, a fault when warm.	—	Bit-encoded
01:06	Short term fuel trim — Bank 1 The module's immediate fuelling correction, moving constantly as the oxygen sensor switches. Positive means it is adding fuel to correct a lean condition. Read alongside long term trim — short term swinging while long term sits high tells a different story from both being high.	%	(A / 1.28) − 100
01:07	Long term fuel trim — Bank 1 The learned, persistent correction the module has settled on. This is the parameter behind P0171 and P0172, and the one worth comparing at idle versus higher load: a vacuum leak drives it strongly positive at idle and less so under load, while a fuel delivery problem does the reverse.	%	(A / 1.28) − 100
01:08	Short term fuel trim — Bank 2 Bank 2's immediate correction. Comparing the two banks is the fastest way to separate a bank-specific fault from a shared one.	%	(A / 1.28) − 100
01:09	Long term fuel trim — Bank 2 Bank 2's learned correction. Both banks drifting together points at the airflow sensor, fuel pressure or the evaporative system; one bank alone points at that bank's injectors, gasket or sensor.	%	(A / 1.28) − 100
01:0A	Fuel pressure Gauge fuel pressure, where a sensor is fitted. Coarse resolution compared with the dedicated rail pressure PIDs, and absent on many vehicles.	kPa	A × 3
01:22	Fuel rail pressure relative to manifold Rail pressure measured relative to manifold vacuum, which is what actually determines injector flow. More diagnostically meaningful than absolute pressure on port-injected engines.	kPa	0.079 × ((256 × A) + B)
01:23	Fuel rail gauge pressure Rail pressure for direct injection and diesel systems, where pressures run far higher. Compare commanded against actual across the load range — that comparison is the core of diagnosing P0087 and P0088.	kPa	10 × ((256 × A) + B)
01:2F	Fuel tank level input Fuel level as a percentage. More than a gauge reading — several monitors are inhibited when the tank is very low or very full, which is why some faults will not reproduce until the level is right.	%	A × 100 / 255
01:44	Commanded air-fuel equivalence ratio Target mixture expressed as lambda, where 1.0 is stoichiometric. Reading the target alongside what the wideband sensor actually reports is how you tell a fuelling problem from a sensor problem.	λ	((256 × A) + B) × 2 / 65536
01:51	Fuel type Declared fuel type. Worth confirming on flexible-fuel and dual-fuel vehicles, since it changes which monitors run and what mixture targets apply.	—	Enumerated
01:52	Ethanol fuel percentage Measured ethanol content. A value that never changes after refuelling with a different blend indicates the composition sensor has stopped responding.	%	A × 100 / 255
01:59	Fuel rail absolute pressure Absolute rail pressure on high-pressure systems. The parameter to watch when diagnosing the P0087 to P0094 group, and the one to compare against an independent gauge when a drifting sensor is suspected.	kPa	10 × ((256 × A) + B)
01:5D	Fuel injection timing When injection occurs relative to top dead centre. On a diesel this governs combustion noise, emissions and peak cylinder pressure, so a deviation is heard as much as measured.	°	(((256 × A) + B) / 128) − 210
01:5E	Engine fuel rate Instantaneous fuel consumption. Comparing this against expected consumption at a known load is a quick way to confirm that a suspected rich condition is real rather than inferred from trim values.	L/h	((256 × A) + B) / 20

Trouble codes

Critical 2

High 300

Moderate 182

Low 11

Information, not instruction

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