232 Code On 95 850 Non Turbo

[MichaelH]

Background: High Mileage 1995 850 Non Turbo, Gas Mileage & Engine Performance Good, Vacuum Elbows seen to be ok.

Have replaced mass air flow sensor and cleared code but engine light will soon come on again with 232 code.

Any ideas?

[AlvinL]

DTC information 2-3-1, 2-3-2

Condition

The control module receives information from the HO2S about the fuel/air mixture in the idling and partial load ranges. If the fuel/air mixture deviates from λ=1 the short term fuel trim will compensate this by adjusting the injection timing so that λ=1 is achieved. When the short term fuel trim carries out this adjustment, its mid–point must be adapted by the long term trim. When the long term fuel trim has adapted the short term trim to a maximum value, DTC 2–3–2 (idling range – 0.48 ms to +0.40 ms) or DTC 2–3–1 (partial load range 0.773 to 1.227) and status message Upper Limit (lean fuel/air mixture) or Lower Limit (rich fuel/air mixture) will be set.

Possible source

Upper limit:

-Defective MAF sensor.

-Low fuel pressure.

-Air leakage.

-Faulty sensor signals.

Lower limit:

-Defective MAF sensor.

-Air leakage.

-High fuel pressure.

-Leaking injectors.

-Leaking EVAP system.

-Dirty engine oil.

-Oil level too high.

-Faulty sensor signals.

Fault symptom-Can result in high fuel consumption.

-Can result in impaired performance.

Code 2-3-1 (Long Term Fuel Trim Partial Load) Or

Code 2-3-2 (Long Term Fuel Trim Idling)

1) Check for other codes. If Code 3-1-5 is stored, performtesting on that code first. If Code 3-1-5 is not stored, go to next

step.

2) Check status message on Volvo Scan Tool (998-8686). If status message reads LOWER LIMIT, go to step 8). If status message reads UPPER LIMIT, go to next step.

3) Turn ignition on. Connect voltmeter between MAF sensor connector terminals No. 2 and 4. If voltmeter reads .1-.2 volt, go to

next step. If voltmeter does not read .1-.2 volt, test using new MAF sensor.

4) Check for air leakage in intake system. Repair as necessary. If air leakage in intake system is not present, go to next

step.

5) Check for air leakage in exhaust system. If there is no air leakage, go to next step. If there is air leakage, repair as

necessary.

6) Check fuel and residual pressure. If fuel and residual pressure are okay, go to next step. If fuel and residual pressure are

not okay, repair as necessary.

7) Connect breakout box to ECM and check ground connections. See COMPUTERIZED ENGINE CONTROLS in I - SYSTEM/COMPONENT TESTS article. Reconnect ECM. Repair as necessary.

8) If status message reads LOWER LIMIT, turn ignition on. Connect voltmeter between MAF sensor connectors terminals No. 2 and 4. If voltmeter reads .1-.2 volt, go to next step. If voltmeter does not read .1-.2 volt, test using new MAF sensor.

9) Check for air leakage in intake and exhaust system. Repair as necessary. Check fuel and residual pressure. Repair as necessary. If no air leakage and fuel and residual pressure are okay, go to next step.

10) Remove hose leading to intake manifold from EVAP valve. Connect vacuum pump to EVAP valve coupling. If vacuum gauge does not show stable vacuum, repair as necessary. If vacuum gauge does show

stable vacuum, go to next step. Check engine oil and fill as necessary.

11) Start engine and run at idle a few minutes. Using Volvo Scan Tool (998-8686), read off value on SHORT TERM FUEL TRIM and note value. Disconnect and plug crankcase ventilation. Read off value of short term fuel trim once again. If value is more or less unchanged, go to next step. If value rises, engine oil is diluted with fuel. Repair as necessary.

12) Connect breakout box to ECM connector and check grounds. Connect ECM. Check all signals to and from ECM. Repair as necessary.