[tbo_cruiser]

I have seen several mentions of the CEL coming on after not tightening the gas cap sufficiently. What code gets set when this happens?

I have a 97LX with about 73K miles right that I bought about a month ago. Right after I bought it (first time I filled with gas) the CEL came on. The seller had a code reader and it was the infamous P0401 EGR code. Is it possible that this is related to the gas cap. The CEL has come on 3 times, always within 10 miles of filling with gas. Once I reset myself, and once it went off by itself.

[wfd175]

It's been my experience that the loose gas cap can throw a couple different codes. 401 is one of them. I don't think there is a specific loose gas cap cel code, or at least I don't recall seeing one in any posts.

The gas cap is always a good place to start. Just disconnect the battery, give the gas cap a couple of clicks tight and try it again. The cap is supposed to create a sealed fuel system. When I remove mine to fill up, I get a small "hiss" of pressure. If you're not, you may also have a bad cap. The cap can be tested also. It's a cheap place to start. The CEL repair prices goes up from there.

Here is a list of 80 series codes.

P0100: Mass Air Flow Circuit Malfunction: Trouble Areas: open or shot in mass air flow meter circuit; mass air flow meter; ECM

P0101: Mass Air Flow Circuit Range/Performance Problem: Trouble Areas: Mass air flow meter

P0110: Inside air temperature circuit malfunction: Trouble Areas: Open or short in intake air temp. sensor circuit; Intake air temp. sensor; ECM.

P0115: Engine Coolant Temp. Circuit Malfunction: Trouble Areas: Open or shot in engine coolant temp. sensor circuit; Engine coolant temp. sensor; ECM

P0116: Engine Coolant Temp. Circuit Range/Performance Problem: Trouble Areas: Engine coolant temp. sensor; Cooling system.

P0120: Throttle/Pedal Position sensor/Switch "A" circuit Malfunction: Trouble Areas: Open or short in throttle position sensor circuit; throttle position sensor; ECM.

P0121: Throttle/Pedal Position sensor/switch "A" circuit range/performance problem: Trouble Areas: Throttle position sensor

P0125: Insufficient Collant temp. for Closed Loop fuel control: Trouble Areas: Open or short in heated oxygen sensor circuit; heated oxygen sensor.

P0130: Heated Oxygen sensor circuit malfunction (bank 1 Sensor 1): Trouble Areas: heated O2 sensor; fuel trim malfunction.

P0133: Heated Oxygen Sensor circuit Slow response (Bank 1 Sensor 1): Trouble Areas: heated O2 sensor.

P0135: Heated O2 Sensor Heater Circuit malfunction (Bank 1 Sensor 1): Trouble Areas: Open or short in heater circuit of heated O2 sensor; heated O2 sensor heater; ECM.

P0136: Heated O2 sensor circuit malfunction (Bank 1 Sensor 2): Trouble Areas: heated O2 sensor.

P0141: Heated O2 Sensor heater circuit malfunction (Bank 1 Sensor 2): Trouble Areas: Same as P0135.

P0171: System too Lean (Fuel Trim): Trouble Areas: air intake (hose loose); fule line pressure--leak; injector blockage; heated O2 sensor malfunction; mass air flow meter; engine coolant temp. sensor.

P0172: System too rich (Fuel trim): Trouble Areas: fule line pressure; injector leak--blockage; heated O2 sensor malfunction; mass air flow meter; engine coolant temp. sensor.

P0300: Random/mulitple Cylinder misfire detected:
P0301: Misfire detected:
P0302-306: Cylinders 1-6:
Trouble Areas: Ignition system; injector; fuel line pressure; EGR; compression pressure; valve clearance not to specification; valve timing; mass air flow meter; engine coolant temp. sensor.

P0325: Knock sensor 1 circuit malfunction: Trouble Areas: Open or short in knock sensor 1 circuit; knock sensor 1 (looseness); ECM.

P0330: Knock sensor 2 circuit malfunction: Trouble Areas: Same as P0325 except at sensor 2

P0335: Crankshaft position sensor "A" circuit malfunction: Trouble Areas: open or short in crankshaft position sensor circuit for NE signal; crankshaft position sensor for NE signal; starter: ECM.

P0340: Camshaft position sensor circuit malfunction: Trouble Areas: open or short in camshaft position sensor circuit; camshaft position sensor; ECM.

P0385: Crankshaft position sensor "B" circuit malfunction: Trouble areas: Same as P0335 except for the NE2 signals are effected.

P0401: EGR flow insufficient detected: Trouble Areas: EGR valve stuck closed; short in VSV circuit for EGR; open in EGR gas temp. sensor circuit; EGR hose disconnected; ECM.

P0402: EGR Flow excessive detected: Trouble Areas: EGR valve stuck open; EGR VSV open malfunction; open in VSV circuit for EGR; short in EGR gas temp. sensor circuit; ECM.

P0420: Catalyst system efficiency below threshold: Trouble Areas: Three-way catalytic convertor; open or short in heated O2 sensor circuit; heated O2 sensor.

P0500: Vehicle Speed Sensor Malfunction: Trouble Areas: Combinatoin meter; open or short in speed sensor circuit; ECM; vehicle speed sensor.

P0505: Idle Control System Malfunction: Trouble Areas: IAC valve is stuck or closed; open or short in IAC Valve circuit; open or short in A/C signal circuit; air intake (hose loose)

P0510: Closed Throttle Position switch malfunction: Trouble Areas: open in closed throttle position switch circuit; closed throttle position switch; ECM.

P1300: Igniter Circuit Malfunction: Trouble Areas: open or short in IGF or IGT circuit from igniter to ECM; igniter; ECM.

P1335: Crankshaft position sensor circuit malfunction (during engine running): Trouble Areas: open or shot in crankshaft position sensor circuit for NE signal; crankshaft position sensor for NE signal; starter; ECM.

P1520: Stop light switch signal malfunction: Trouble Areas: short in stop light switch signal circuit; stop light switch; ECM.

P1600: ECM BATT malfunction: Trouble Areas: open in back up power source circuit; ECM.

P1605: Knock control CPU malfunction: Trouble Areas: ECM.

P1780: Park/Neutral position switch malfunction: Trouble Areas: short in park/neutral position switch circuit; park/neutral position switch; ECM.

[CJF]

Get a new OEM cas cap. (Should be replace every once in a while anyway.)

Nice, cheap way to see if that's the problem.