ECU "readiness" codes and battery replacement
02-18-2004, 01:03 PM
#1
Nordschleife Master
Thread Starter
ECU "readiness" codes and battery replacement
My battery still appears to be in fine shape, but (being an engineer) I like to have a handle on this kind of stuff. I've heard that when you unpower your car (like disconnect the battery?) the ECU readiness codes get reset, and it takes some very special driving sequences (that you can't duplicate in normal driving) to get them set again. This becomes important when the OBD is used to read the codes when getting a smog test.
Has anybody experienced this issue? Can you prevent this from happening by keeping 12V on the battery cables (using a trickle charger) while changing the battery? Is there a time component involved in the disconnect, such that if you swap the battery "really fast", the ECU doesn't get reset? Can the readiness codes get set via some other method other than the rather bizarre driving sequence? So many questions.... help an engineer.
Has anybody experienced this issue? Can you prevent this from happening by keeping 12V on the battery cables (using a trickle charger) while changing the battery? Is there a time component involved in the disconnect, such that if you swap the battery "really fast", the ECU doesn't get reset? Can the readiness codes get set via some other method other than the rather bizarre driving sequence? So many questions.... help an engineer.
02-18-2004, 01:37 PM
#2
Pro
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Steve,
Yes, we come across this occassionally. for us it is when a car has been sitting on a sales lot, battery totally dead, sell car, smog required.
The only time the "flags" become an issue is when the OBD II car is immediatley taken for smog after the new battery is installed. The car has not had time time to complete the the sequences by normal driving. (In the course of 6-12 months, you will satisfy the sequences and never realize there was a problem). If smog is in a day or week, we perform the sequences manually, usually hooking up the PST as an aide, and get it done quickly.
Your best bet is to keep the 12V on the battery lines and this will maintain the "flags".
Laura
Hergesheimer MotorSports
Yes, we come across this occassionally. for us it is when a car has been sitting on a sales lot, battery totally dead, sell car, smog required.
The only time the "flags" become an issue is when the OBD II car is immediatley taken for smog after the new battery is installed. The car has not had time time to complete the the sequences by normal driving. (In the course of 6-12 months, you will satisfy the sequences and never realize there was a problem). If smog is in a day or week, we perform the sequences manually, usually hooking up the PST as an aide, and get it done quickly.
Your best bet is to keep the 12V on the battery lines and this will maintain the "flags".
Laura
Hergesheimer MotorSports
02-18-2004, 01:46 PM
#3
Burning Brakes
Join Date: Aug 2003
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Laura,
Is this an issue on the OBD I cars like the '95? I am about to change steering wheels and was going to disconnect the battery for about a hour then do the swap, and hook up again.
Any issues I should be aware of?
TIA
Is this an issue on the OBD I cars like the '95? I am about to change steering wheels and was going to disconnect the battery for about a hour then do the swap, and hook up again.
Any issues I should be aware of?
TIA
Last edited by Evan; 02-18-2004 at 02:06 PM.
02-18-2004, 01:57 PM
#4
Racer
This is an OBDII issue - '96 on.
Readiness code reset routine:
Start engine, idle cold for approx. 2 min, 10 secs.
Accelerate to 20-30 MPH, Maintain steady speed for approx 3 min, 15 secs.
Accelerate to 40-60 MPH, Maintain steady speed for approx 15 mins.
Decelrate and come to a stop. Idle in gear for approx 5 mins.
Following the start engine phase the sequence of test conditions may interchange.
routine will be discountinued whenever:
Engine speed exceeds 3000 RPM
Large fluctuations in throttle angle
Road speed exceeds 60 MPH
Readiness code reset routine:
Start engine, idle cold for approx. 2 min, 10 secs.
Accelerate to 20-30 MPH, Maintain steady speed for approx 3 min, 15 secs.
Accelerate to 40-60 MPH, Maintain steady speed for approx 15 mins.
Decelrate and come to a stop. Idle in gear for approx 5 mins.
Following the start engine phase the sequence of test conditions may interchange.
routine will be discountinued whenever:
Engine speed exceeds 3000 RPM
Large fluctuations in throttle angle
Road speed exceeds 60 MPH
