b-dub

Took my 97 Z28 in for smog test.
Failed with a P1441 code. Replaced EVAP Canister Purge Valve and am now told I have to drive a very specific way to reset computer.
ie drive 35 mph for 10 minutes then 55 mph for ten minutes then idle for a few minutes etc etc etc...
Has anyone here gone through this and if so can you tell me the specifics

of this procedure?

DrewHMS97SS

There isn't any special way to drive it, just get enough drive cycle in for all of the sensors to pass. If you drive between 25-50 miles, you should be fine.

Injuneer

From the 1996 factory service manual (99% same as 1997):for DTC P1441


CONDITIONS FOR CLEARING THE MIL/DTC:

- The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail

- A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.

- A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

- PCM battery voltage is interupted

- Using a Scan tool.

CONDITIONS FOR (running diagnostic and) SETTING THE DTC:

- Numerous other DTC's can not be set.

- ECT less than 239-degF

- IAT greater than 37-degF

- Engine speed between 500 - 3000 RPM

- TP angle less than 50%

- MAP less than 70 kPa

- Barometer greater than 77 kPa

- Purge not enabled

- Code sets if PCM detects high signal voltage on the EVAP vacuum switch signal angle when the PCM is not commanding purge on, for 5 seconds.



Was the purge solenoid stuck open? Are you sure the lines connected to the purge solenoid are in the correct position - line to throttle body on top connection, line from canister on bottom connection (from Shoebox)?

http://shbox.com/1/1996_evap.jpg

Chimera96

OP

regarding the "drive cycle" to reset the GM PCM so all IM monitors read ready (disconnecting the battery or clearing any code kills all IM monitor ready function) basically requires you do it on a closed course as the steps can be dangerous on public roads

Your code though "should" clear with a few drive cycles on city and hwy driving ...its the IM readiness that will take time and some may never reset if you have a modified motor (EGR and CAT Heat) which depending on your state and emission laws can be a challange....without doing "alternative" programming to the PCM (cough)

GM drive cycle:

General Motors Driving Cycle

A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle do the following:

1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
4. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
6. Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
7. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
8. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

b-dub

Hi Fred

Thanks for the reply. The EVAP solenoid was stuck open and has been replaced correctly. Am now trying to determine the best way to accomplish drive cycle . I am thinking that taking it to a dyno shop is my only hope.

Bill

b-dub

Thanks for the reply Chimera96. Am headed to the local dyno shop with this info in hand. wish me luck...

Bill

Chimera96

That's a lot of dyno time...good luck.

when you clear any OBD2 code using a scan tool or disconnecting the battery all the IM monitors need to be reset by the drive cycle

The alternative is have a tuner set all the IM as "ready" all the time....or so I have read (cough) :-)

then disconnecting battery for any reason will have no affect and the IM will show "ready" when battery is hooked up. Otherwise you need to do the whole "drive cycle" again. EGR and CAT Heat are typically the two hardest ones to get to reset ready especially with camed motors. Even when EGR & CATS are functioning right. Unfortunately 1/1/2018 BAR changed the emission laws to only allow 1 IM monitor to read not ready, vs 2 previously if you live in CA

Since you just had a 1441 code and fixed the problem you could just drive a few days and use a scanner that shows IM functions as being ready will show if they are if you have a stock motor