goofy123

Hi guys

Just bought a 1996 Altima which has a few problems as listed below:

1. Error Code P1400, EGR-Solenoid valve Circuit using generic scanner
2. When I turn the key to on position the MIL light does not light up for bulb check but lights up sometimes when car is running. Also when I run the car the MIL is generally flashing instead of being steady.
3. Fuel gauge does not ready full tank even when fuel seems to be fully filled in.
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I did the following as per the service manual:

1. Checked input voltage from ECM to sub-harness connector of EGR Solenoid valve - OK
2. Checked connectivity on the output side of EGR solenoid valve sub harness connector and ECM connector - OK
3. Checked Solenoid valve functionality by applying 12V DC - Valve ok
4. Checked ECM pins - no bends or broken pins

in the manual it is mentioned that I need to check connectivity between EGR solenoid valve harness and the EGR solenoid valve - I did not find any connectivity- Does this mean the ECM is bad and not recognising the output from solenoid?

Checked EGR valve by lightly lifting the diaphragm during idle, engine stalls, hence concluded EGR valve is not held up and seated properly. Also removed and checked seat and valve seemed ok.

If I have to replace the ECM harness or ECM, how big a job is this? Is there a way to check ECM functionality?

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My scanner cannot be used during engine running mode. I suspect misfiring may be the cause of MIL flashing -- which in turn can be caused by EGR solenoid valve malfunction. That is my understanding correct me if I am wrong here. Also as per the service bulletin there may be misfiring due to bad plug wires. Will install new plug wires to check the same.
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for replacing fuel sending unit do I have to take the fuel tank down.
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One more thing - Are there more than one filament in the MIL bulb? and if the bulb check fails does it in any way cause the ECM to be in a not ready mode?
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Thanks