VOLVO
ECM-644A - Reset valve, camshaft. Slow regulation/Faulty signal. Intermittent fault
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), V70 (1997–2000), V70 XC (1998–2000)
Show models by year and engine (10)
- Volvo C70 Cabriolet (1998–2005)1999, 2001–2002
- Volvo C70 Cabriolet (1998–2005)2000All engines except: B5244S
- Volvo C70 Coupé (1998–2002)1999All engines except: B5254S DENSO
- Volvo C70 Coupé (1998–2002)2000All engines except: B5244S
- Volvo C70 Coupé (1998–2002)2001–2002
- Volvo S70 (1997–2000)1999Engine B5204T3, B5204T4, B5234T3, B5234T7, B5254T only
- Volvo S70 (1997–2000)2000Engine B5204T3, B5204T4, B5234T3, B5234T7, B5244T only
- Volvo V70 (1997–2000)1999Engine B5204T3, B5204T4, B5234T3, B5234T7, B5234T8, B5254T only
- Volvo V70 (1997–2000)2000All engines except: B5244S, B5244S2, B5244SG, B5244SG2, D5252T MSA 15.8
- Volvo V70 XC (1998–2000)1999–2000
What does this fault code mean?
The reset valve for the camshaft is regulating too slowly or giving a faulty signal. The fault is intermittent, meaning it comes and goes, so it may be gone when you check. The variable camshaft is switched off while the fault is present, which can show up as poorer performance.
Possible causes
- The timing belt has jumped over the teeth
- Defective reset valve
- Mechanical fault in the VVT unit
- Defective camshaft position sensor
- Low oil pressure
- Poor oil quality
What you can do
- 1Check the engine oil level and quality, and look for contamination
- 2Use a multimeter to check that the wiring to the camshaft sensor and reset valve has no open circuit or short to ground or supply voltage
- 3Have a workshop clean the reset valve and check the oil passages in the cylinder head. Replace the valve if it is contaminated
- 4With a diagnostic tool, compare the actual camshaft position with the target at idle, but only once the engine speed has stabilised
- 5If the fault remains after this, the VVT unit may be damaged, which a workshop needs to assess
Symptoms you may notice1
- Poorer performance
What the fault can affect1
- The variable camshaft is switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.