Faulty camshaft position sensor or crankshaft position sensor, providing erratic signals; Worn or stretched timing chain/belt, causing a mechanical timing offset; Contaminated or failing fuel injectors, leading to inconsistent injection start; Electrical issues such as damaged wiring or corroded connectors to the injectors or sensors; Sticking or faulty injection pump (on diesel engines), affecting injection timing; Carbon buildup on intake valves or injector tips, altering spray patterns; ECM software calibration issues or internal faults (less common)

DTC codes / Volkswagen codes / P1248

P1248 · VolkswagenInjection Start Control Deviation

Q: What does code P1248 mean?

Injection Start Control Deviation. P1248 on Volkswagen vehicles indicates that the engine control module (ECM) has detected a deviation between the commanded injection start and the actual injection start timing, typically monitored via the camshaft position sensor compared to the crankshaft position sensor. This means the ECM cannot reliably confirm that the fuel injectors are opening at the precise moment required for optimal combustion, which can affect performance and emissions.

P1248 on Volkswagen vehicles indicates that the engine control module (ECM) has detected a deviation between the commanded injection start and the actual injection start timing, typically monitored via the camshaft position sensor compared to the crankshaft position sensor. This means the ECM cannot reliably confirm that the fuel injectors are opening at the precise moment required for optimal combustion, which can affect performance and emissions.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyProfessional

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or intermittent misfire, especially when the engine is cold
Reduced engine power or hesitation during acceleration
Poor fuel economy due to inefficient combustion
Hard starting or extended cranking before the engine fires
In rare cases, the engine may enter limp mode to protect the catalytic converter

Common causes, most likely first

Faulty camshaft position sensor or crankshaft position sensor, providing erratic signals
Worn or stretched timing chain/belt, causing a mechanical timing offset
Contaminated or failing fuel injectors, leading to inconsistent injection start
Electrical issues such as damaged wiring or corroded connectors to the injectors or sensors
Sticking or faulty injection pump (on diesel engines), affecting injection timing
Carbon buildup on intake valves or injector tips, altering spray patterns
ECM software calibration issues or internal faults (less common)

How to diagnose and fix it

Perform a visual inspection of the engine wiring harness and connectors for damage or corrosion
Use a scan tool to check for related fault codes and freeze-frame data to identify when the deviation occurs
Verify sensor signals with an oscilloscope to compare camshaft and crankshaft position sensor waveforms
Check the timing chain/belt for stretch or misalignment using manufacturer procedures
Test fuel injectors for resistance, spray pattern, and flow rate; clean or replace as needed
Inspect and test the injection pump (diesel) for proper timing and function
Update the ECM software if a known calibration issue exists, or replace the ECM if internal fault is confirmed

Before you replace the camshaft sensor

A stretched timing chain is a common cause on higher-mileage Volkswagen engines, and replacing sensors alone will not fix the deviation.
The code can be set by a weak battery or charging system issue that causes voltage drops, leading to erratic sensor signals.
On some TDI engines, a clogged fuel filter or air in the fuel system can mimic injection timing problems and set P1248.
Always check for technical service bulletins (TSBs) specific to your engine code; some require a software update rather than hardware replacement.
P1248 can be a stored code from a previous repair that was not cleared, so always clear codes and verify if it returns before diagnosing.

Can I keep driving with P1248?

You can generally drive the vehicle with P1248, but avoid aggressive acceleration or heavy loads until the fault is diagnosed, as prolonged driving with incorrect injection timing may damage the catalytic converter or cause engine performance issues.

Tools that help

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Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.