VOLVO
ECM-4038 - Brake vacuum. Too low vacuum
System
Engine Control Module (ECM)
Volvo models this fault code applies to
This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.
Applies to the following models:
5 modelsC70 Cabriolet (1998–2005), C70 Coupé (1998–2002), S70 (1997–2000), S80 (1999–2006), V70 (1997–2000)
Show models by year and engine (8)
- Volvo C70 Cabriolet (1998–2005)2000Engine B5244S only
- Volvo C70 Coupé (1998–2002)1999Engine B5254S DENSO only
- Volvo C70 Coupé (1998–2002)2000Engine B5244S only
- Volvo S70 (1997–2000)1999Engine B5252FS, B5254S DENSO only
- Volvo S70 (1997–2000)2000Engine B5244S, B5244S2, B5244SG, B5244SG2 only
- Volvo S80 (1999–2006)1999–2000Engine B5244S, B5244S2 only
- Volvo V70 (1997–2000)1999Engine B5254S DENSO only
- Volvo V70 (1997–2000)2000Engine B5244S, B5244S2, B5244SG, B5244SG2 only
What does this fault code mean?
The engine control module monitors that the engine can supply the brake booster with enough vacuum. The fault code is set when the difference between the intake manifold pressure and the air pressure around the car is too small while the airflow into the engine is too high. The code usually appears together with other fault codes that point to an airflow problem, and those should be checked first.
Possible causes
- Air leak at the joint between the throttle body and the cylinder head
- Blocked, condensed or dirty lines running from the pressure sensor to the intake manifold
- Fault in the throttle unit or its throttle control
- Incorrect signal from the pressure sensor
What you can do
- 1Check other fault codes in the engine control module first, especially those for the throttle or airflow, since this code is often a result of them
- 2Make sure there is no air leak at the joint between the throttle body and the cylinder head
- 3Inspect the vacuum lines running from the pressure sensor to the intake manifold for blockage, condensation and dirt
- 4Have you got a diagnostic tool: compare the intake manifold pressure with the air pressure around the car at idle and check that they differ
- 5Switch off the ignition and wait until the throttle control module has shut down, then cycle the ignition and wait again before rechecking
- 6Have a workshop check whether the engine control module has the upgraded software from 2006 or later, and load it if it is missing
Symptoms you may notice2
- Uneven idle
- Poorer performance at high speed
What the fault can affect3
- Cruise control is switched off during the operating cycle in which the fault was detected, and works again at the next start if the fault is gone
- Engine speed is controlled by cutting fuel to the cylinders one at a time, and the speed is limited
- The uneven idle may come from this reconfiguration rather than from a real drivability fault that existed before
General guidance for car owners. Diagnosis on the car can point to a different cause.