|Code||Fault Location||Probable Cause|
|P0149|| Fuel timing error |
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|Fuel pump/fuel injection pump|
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What Does Code P0149 Mean?
Some diesel engines use a distributor injection mechanical fuel pump to generate the high pressures required to inject fuel directly into the cylinder under compression and are usually driven directly by the timing chain. Each pulse of the fuel pump is timed to coincide with an injection pulse, and can provide as much as 300 MPa (3,000 bar or 44,000 psi) to the fuel injectors. This type of fuel pump is very compact, including both low- and high-pressure pumps and fuel pressure regulating device.
Injection pump timing and pressure is directly related to engine speed because it is driven by the timing chain, so there must be a way to advance injection timing. This is accomplished by the fuel timing device, which changes the rotation of the pump outlets in relation to the input drive. In most modern vehicles, injector advance, that is, fuel timing, is controlled by the fuel timing solenoid valve, which is controlled by the ECM (engine control module), based on engine speed and load. Fuel timing can be advanced by as much as 25° BTDC (before top dead center), when measured from the crankshaft.
The ECM uses fuel pressure readings to modulate fuel pressure, via the fuel pressure regulator, as well as to monitor the function of the fuel pump itself. If the ECM detects a problem in the timing of the pulses, it interprets this as a fault, setting a DTC (diagnostic trouble code). DTC P0149 is defined as “Fuel Timing Error.”
What are the common causes of code P0149 ?
Depending on year, make, and model, DTC P0149 may have number of causes. Here are some of the most common.
- Fuel Timing Solenoid – Failure of the solenoid is the most common problem experienced by drivers. It is usually held in by 2 or 3 bolts and sealed by a couple of o-rings. The part may be available separately from the fuel pump assembly, though it may require rewiring from the controller or ECM to the new solenoid.
- Mis-Timing – If crankshaft / fuel-pump correlation is off by even one tooth, this will cause fuel timing problems that the ECM cannot compensate for.
What are the symptoms of code P0149 ?
Depending on the failure mode and the vehicle, the ECM may illuminate the MIL (malfunction indicator lamp) and may put the vehicle into “limp-home” mode. If you can start the vehicle, at the very least, you’ll note a decline in fuel economy and engine performance, particularly at high speed or high load. On the other hand, you may not be able to start the engine at all, as the ECM attempts to protect itself and the high-pressure fuel pump from damage.
How do you troubleshoot code P0149 ?
This problem can be caused by two main faults: mechanical timing or electrical fault. Because electrical fault is easier to check, you should definitely do that first. One exception to this might be if you have recently had engine work done that required the removal of the timing chain. Diagnose and repair any other fuel system DTCs before addressing this problem.
- General Check – Check that there are no fuel leaks or damaged fuel system components, repair as needed.
- Fuel Timing Solenoid – The fuel timing solenoid is located on the lower part of the fuel pump assembly and may be connected directly to the ECM or to a sub-controller. If there are communication codes for the sub-controller, diagnose and repair these first.
- Check for obvious damage in the wire harness between the ECM and fuel timing solenoid. Repair as needed.
- If you can disconnect the fuel timing solenoid, use a DMM (digital multimeter) to measure the resistance across the terminals. Resistance should measure between 10 Ω and 20 Ω across the coil and over 10 kΩ to ground. Replace if resistance is not as specified.
- NOTE: If you cannot disconnect the fuel timing solenoid, do not attempt to check resistance – you can fry the sub-controller. A factory scan tool may give you access to active testing capabilities, such as manually activating the fuel timing solenoid.
- Mechanical Check – It’s highly unlikely that a timing chain may “skip time” or stretch enough to cause a fuel timing problem – a stretched chain would cause a crankshaft-camshaft correlation fault. More likely is a problem during any recent operation that required the removal of the timing chain. Checking time between the crankshaft and fuel pump will require the removal of multiple parts. Make sure that all the timing marks – on the chain, sprockets, engine block, and cylinder head – are lined up perfectly. Repair as necessary.