Here is my semi-educated info, specific instructions beyond “just drive it” and experience on passing smog in California.
If the Battery has been disconnected for replacement, service or if the codes have been cleared, the car may pass the emissions test but fail the OBD II systems test. Evidentially you need to get the system to exercise the Monitors and components with specific driving modes.
My ’97 Spa Yellow failed smog (since the battery was disconnected for a regular service) and a check with my Autel AL619 tester ($135 at Amazon) showed:
MIL Status Off (check engine light is off)
Codes Found 0 (no system faults found)
Monitors N/A 2 (I think this means 2 monitors are not needed or used on this vehicle) Help on this from anyone?
Monitors OK 4 (4 Monitors are registering and are ok)
Monitors Inc 4 (4 Monitors are Incomplete and have not been checked by the ODB II system)
Incomplete are: Catalyst; EVAP Sys Mon; O2 Sensor; EGR
This is where the Smog test failure is, as Calif. allows only 2 Monitors to register incomplete.
To pass, I need to get 2 Monitors reading the systems and “OK”.
To do this I went to the OBD Drive Cycle info I found on PRIME (thank you to whoever posted it). This forum is GREAT.
___________________________________________
The OBDII drive cycle begins with a cold start (coolant temperature below 122 degrees F and the coolant and air temperature sensors within 11 degrees of one another).
NOTE: The ignition key must not be on prior to the cold start otherwise the heated oxygen sensor diagnostic may not run.
Fuel tank should be between 3/4 and 1/4
1) As soon as the engine starts, idle the engine in drive for two and a half minutes with the A/C and rear defrost on. OBDII checks oxygen sensor heater circuits, air pump and EVAP purge.
(ChrisW Note: I idled my 6 speed in Neutral)
2) Turn the A/C and rear defrost off, and accelerate to 55 mph at half throttle. OBDII checks for ignition misfire, fuel trim and canister purge.
3) Hold at a steady state speed of 55 mph for three minutes. OBDII monitors EGR, air pump, O2 sensors and canister purge.
4) Decelerate (coast down) to 20 mph without braking or depressing the clutch. OBDII checks EGR and purge functions.
5) Accelerate back to 55 to 60 mph at ¾ throttle. OBDII checks misfire, fuel trim and purge again.
6) Hold at a steady speed of 55 to 60 mph for five minutes. OBDII monitors catalytic converter efficiency, misfire, EGR, fuel trim, oxygen sensors and purge functions.
7) Decelerate (coast down) to a stop without braking. OBDII makes a final check of EGR and canister purge.
Note: after doing items 1-4 I hooked up my tester that showed O2 Sensor and EGR as OK. I had the system checked by a smog station and it passed!
Hopefully this helps with specific instructions. Since no one ever drives like the above it is no wonder “just drive it“ does not exercise the system. I have the 3” thick shop manual and cannot find “Drive Cycles” listed anywhere in it. If anyone has found it please post it.
Good luck to everyone.
If the Battery has been disconnected for replacement, service or if the codes have been cleared, the car may pass the emissions test but fail the OBD II systems test. Evidentially you need to get the system to exercise the Monitors and components with specific driving modes.
My ’97 Spa Yellow failed smog (since the battery was disconnected for a regular service) and a check with my Autel AL619 tester ($135 at Amazon) showed:
MIL Status Off (check engine light is off)
Codes Found 0 (no system faults found)
Monitors N/A 2 (I think this means 2 monitors are not needed or used on this vehicle) Help on this from anyone?
Monitors OK 4 (4 Monitors are registering and are ok)
Monitors Inc 4 (4 Monitors are Incomplete and have not been checked by the ODB II system)
Incomplete are: Catalyst; EVAP Sys Mon; O2 Sensor; EGR
This is where the Smog test failure is, as Calif. allows only 2 Monitors to register incomplete.
To pass, I need to get 2 Monitors reading the systems and “OK”.
To do this I went to the OBD Drive Cycle info I found on PRIME (thank you to whoever posted it). This forum is GREAT.
___________________________________________
The OBDII drive cycle begins with a cold start (coolant temperature below 122 degrees F and the coolant and air temperature sensors within 11 degrees of one another).
NOTE: The ignition key must not be on prior to the cold start otherwise the heated oxygen sensor diagnostic may not run.
Fuel tank should be between 3/4 and 1/4
1) As soon as the engine starts, idle the engine in drive for two and a half minutes with the A/C and rear defrost on. OBDII checks oxygen sensor heater circuits, air pump and EVAP purge.
(ChrisW Note: I idled my 6 speed in Neutral)
2) Turn the A/C and rear defrost off, and accelerate to 55 mph at half throttle. OBDII checks for ignition misfire, fuel trim and canister purge.
3) Hold at a steady state speed of 55 mph for three minutes. OBDII monitors EGR, air pump, O2 sensors and canister purge.
4) Decelerate (coast down) to 20 mph without braking or depressing the clutch. OBDII checks EGR and purge functions.
5) Accelerate back to 55 to 60 mph at ¾ throttle. OBDII checks misfire, fuel trim and purge again.
6) Hold at a steady speed of 55 to 60 mph for five minutes. OBDII monitors catalytic converter efficiency, misfire, EGR, fuel trim, oxygen sensors and purge functions.
7) Decelerate (coast down) to a stop without braking. OBDII makes a final check of EGR and canister purge.
Note: after doing items 1-4 I hooked up my tester that showed O2 Sensor and EGR as OK. I had the system checked by a smog station and it passed!
Hopefully this helps with specific instructions. Since no one ever drives like the above it is no wonder “just drive it“ does not exercise the system. I have the 3” thick shop manual and cannot find “Drive Cycles” listed anywhere in it. If anyone has found it please post it.
Good luck to everyone.
Last edited:
