2001 Volvo S40 CEL

WG

MEMBER
2001 VOLVO S40
4 CYL
FWD
AUTOMATIC
120 MILES

Girlfriend's 2001 Volvo S40 w/ 120K miles getting multiple OBD II error codes, P0015, P0015-pd, & P0420. Can't speak for maintenance history but suspect some neglect. Are the camshaft position sensor and CAT both shot? Just changed oil & added SeaFoam to try and clean any possible clogged oil ports. Also noticed oil dipstick O-ring was misshapen.
Engine starts Ok - maybe a little longer cranking than I would like to see. Where else do I look before she starts replacing $175 sensors and $250 cats?

1 Reply

JIS001

MECHANIC
3,408 POSTS

Here is a description for fault code PO420

Condition
The three-way catalytic converter (TWC) efficiency is checked once every driving cycle. The control module applies a different cycle to the front heated oxygen sensor (HO2S). Diagnostic trouble code (DTC) ECM-5A is stored and the rear heated oxygen sensor (HO2S) signal is altered if the three-way catalytic converter (TWC) efficiency is diminished.

Substitute Value
None.

Possible Source

Uneven compression.
Air leakage in the intake system.
Leakage in the exhaust system.
Faulty fuel pressure.
Defective three-way catalytic converter (TWC).
Fault Symptom[s]

May result in poor performance.

Look for an exhaust leak to be the root cause of the fault. The exhaust nuts/studs start to back out and even fall out. That leak causes the oxygen sensors to give a faulty reading due to the unmetered air going in.