captain_anchovy
have had 95 850 non turbo for a couple of months.
notice soot in tail pipe and very heavy on fuel.
Volvo Guru showed me how to read codes. got, among others a 2 1 2 and a 5 2 1. Front O2 sensor signal and pre heat.
replaced O2 sensor with an EBay special. now only getting the 5 2 1. pre heat. still have the soot and still heavy on fuel. pulled spark plug. soot as well.
any idea as to what i should do next ?
Thanks.
Ex850R
Get new Volvo plugs.
Rotor and cap ok?
captain_anchovy
Don't want to appear ignorant but how would plugs,leads etc. Affect the code?
As a matter of interest the leads and cap look original. IE 21 years old. Plugs are new NGK
timbo
Whiteblocks prefer genuine volvo plugs the non turbo 850 have a triple electrode style. There is a fuse for the 02 pre-heater circuit have you checked that yet?
Coolant temp sensor could be suspect too
captain_anchovy
Yes checked fuse. The NGK plugs are double electrode. Any easy way to check coolant sensor ?
captain_anchovy
Re fuse. Was told it was 32 or 33. Can you confirm that ?
Ex850R
Whiteblock motors like Volvo brand plugs and Bougicord leads only.
Do the cap and rotor while there.
CTS is a usual culprit too.
Blocked cat?
MAF good?
Ex850R
And no, there are no ignorant questions here.
Just helpful answers.
If you don't ask.... You never learn
captain_anchovy
Er "CTS". What that?
captain_anchovy
Re Cat. The DPO Has cut the cat open and welded it shut again. The car id quite LOUD so perhaps nothing inside the cat.
nickm
Coolant temp sensor.
If it is running rich I would also check the fuel regulator.
the O2 code could be a symptom not the cause.
Ex850R
Could be that the "de-cat" has thrown the code. Spacing out one of the O2 sensors fixes decat, the back one? Not sure.
captain_anchovy
just rechecked fuse. fuse good but nil volts going to it.
nickm
here is a good synopsis
"The below info is courtesy of Alldata Inc....
Hopefully it will help you out...
Condition
Probe monitoring begins after probe preheating diagnostics are complete. Diagnostic Trouble Code (DTC) ECM-280A is stored if there is a fault in the front Heated Oxygen Sensor (HO2S) or its wiring causing the signal to deviate from its permitted range
The control module registers four different types of fault:
•Signal too high The control module compares the front and rear adaptation values. A Diagnostic Trouble Code (DTC) is stored when the values deviate by more than 3%.
NOTE: The fault may be in the front or rear Heated Oxygen Sensor (HO2S) circuit.
•Signal too low The control module monitors the aging of the probe by checking its dynamics when switching between lean and rich mixtures. The Diagnostic Trouble Code (DTC) is stored if the control module registers that the probe is operating too slowly.
•Signal missing The control module monitors cross-induction from the probe preheating. Diagnostic Trouble Code (DTC) is stored when cross induction exceeds the permitted value.
•Faulty signal A Diagnostic Trouble Code (DTC) stored when:
•the control module registers that the signal from the front probe is above 4.8 V for too long
•the signal from the front probe does not deviate from [lambda] = 1
•the signal from the front probe is showing a lean fuel mixture while the signal from the rear probe is showing a rich mixture
•the signal from the front probe is showing a rich fuel mixture while the signal from the rear probe is showing a lean mixture.
Condition
•The rear Heated Oxygen Sensor (HO2S) control is disabled
•Three-way catalytic converter (TWC) diagnostic is disabled
Possible source
Signal too high:
•air leakage in the exhaust system
•short-circuit to power supply or ground in the signal cable (+) or supply cable for pump current
•defective Heated Oxygen Sensor (HO2S)
Signal too low:
•the cable for calibration current and the cable for pump current are short-circuited to each other
•open-circuit in signal cable (-)
•open-circuit in cable for calibration current
•defective Heated Oxygen Sensor (HO2S).
Signal missing:
•signal cable (+) and signal cable (-) short-circuited to each other
•one of the cables for Heated Oxygen Sensor (HO2S) preheating is short-circuited to the probe's other wiring
•defective Heated Oxygen Sensor (HO2S).
Faulty signal:
•short-circuit to supply voltage or ground in signal cable (+)
•short-circuit to supply voltage or ground in signal cable (-)
•short-circuit to supply voltage or ground in pump current cable
•short-circuit to supply voltage or ground in calibration current cable
•open-circuit in signal cable (+)
•defective Heated Oxygen Sensor (HO2S).
Condition
•Malfunction Indicator Lamp (MIL) lit.
nickm
According to the wring diagram you pull voltage from the fuel pump relay
captain_anchovy
can anyone who has a wiring diagram tell me where power comes to and goes from fuse 33 ?
nickm
captain_anchovy
OBD ?
captain_anchovy
Oh that OBD ? Yes little black box. Push button and count flash.
nickm
Seems something is different between the 1996 and the model before at that fuse.
It looks like pre 1996 models pull voltage for the OBD box from there.
What are you chasing?
