2001 Silverado ECM stuck in test mode
09-05-2008, 01:17 PM
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2001 Silverado ECM stuck in test mode
I have a 2001 Silverado 1500 w/ 150k on it. I just went to have it inspected, and the computer says my ECM is stuck in test mode for 2 monitors. The Evap system, and Catalyst system. It is doing the same thing after I put another ECM in. No codes are showing, and the SES light is not on. Any help would be greatly appreciated. Thanks in advance.
Bill
Bill
09-05-2008, 02:03 PM
#2
Sounds like the EVAP and Catalyst monitors just haven't completed their tests, which is normal operation. The truck needs to be driven and certain parameters have to be met for those monitors to run, (certain ambient temp, fuel level between 1/4 and 3/4 tank, vehicle must reach a certain speed and maintain it for a period of time, etc.), then the PCM has to be scanned, without turning the key off or the monitors will clear and will have to run again. Vehicles fail inspection for incomplete monitors all the time...
09-05-2008, 02:21 PM
#3
Here's some info that I copied and pasted after a google search in reference to the monitor's readiness status, hope this helps:
READINESS ISSUES
One of the EPA's requirements for using a plug-in OBD II check in lieu of a tailpipe test is to make sure the OBD II system has run all of its monitors and that the monitors have all passed. But there's a catch. Some import vehicles have readiness issues when it comes to setting all the OBD II monitors. Consequently, the EPA currently allows up to two readiness monitors not to be set prior to testing 1996 to 2000 model-year vehicles, and one readiness monitor for 2001 to 2003 vehicles.
When OBD II runs a self-check on a particular component or system, it lets you know by setting a readiness "flag" or indicator, which can be displayed on your code reader or scan tool. If OBD II has run all the available monitors and all the monitors have passed (and no faults have been found) the vehicle should pass the OBD II plug-in test. But if all the required monitors have not run, the vehicle canno be given an OBD II test. The motorist must drive the vehicle and come back again, or take a tailpipe test if that is an option.
If OBD II detects a fault when running a monitor, the setting of a code may prevent the remaining monitors from running. A bad oxygen sensor, for example, will prevent the catalyst monitor from running. Getting all the monitors to run can be tricky on some vehicles. Each monitor has certain operating requirements that must take place before the self-check will run.
To set the converter monitor, for example, the vehicle may have to be driven a certain distance at a variety of different speeds. The requirements for the various monitors can vary considerably from one vehicle manufacturer to another, so there is no "universal" drive cycle that will guarantee all the monitors will be set and ready.
Mike Cole of the National Center for Vehicle Emissions Control and Safety (NCVECS) at Colorado State University says some vehicles require very specific drive cycles (called "drive traces" if you perform them on a road simulator or dyno) to activate certain self-checks like the catalyst and EVAP monitors. NCVECS has compiled all the known drive traces for various vehicles on a CD and offers the package to technicians for about $40. For more information, you can visit www.ncvecs.colostate.edu.
As a general rule, doing some stop-and-go driving around town at speeds up to about 30 mph, followed by five to seven minutes of steady 55 mph highway speed driving, will usually set most or all of the monitors. Consequently, if you are checking an OBD II system and discover that one or more of the monitors have not run, it may be necessary to drive the vehicle more to set the remaining monitors.
With the EVAP monitor, the vehicle may require a certain period of inactivity (such as sitting overnight) and certain ambient temperature conditions (such as above freezing) before the EVAP monitor will run.
Some vehicles with known readiness issues include 1996 to 1998 Mitsubishi cars (which require a very specific drive cycle), and 1996 Subarus and Volvo 850 Turbos (turning the key off clears all the readiness flags, so don't turn the vehicle off after driving). On 1997 Toyota Tercels and Paseos, the readiness flag for the EVAP monitor never will set, and no dealer fix is yet available. Other vehicles that often have a "not ready" condition for the EVAP and catalytic converter monitors include 1996-1998 Volvos, 1996-1998 Saabs and the 1996-1997 Nissan 2.0L 200SX.
DRIVE CYCLES
If the MIL comes on while driving, or remains on after starting the engine, it means OBD II has detected a problem. The lamp will usually remain on, unless the fault does not reoccur in three consecutive drive cycles that encounter the same operating conditions, or the fault is not detected for another 40 drive cycles. If OBD II sees no further evidence of the problem, it will turn off the MIL and erase the code.
An OBD II drive cycle is not just turning the ignition key on and off or starting the engine. A drive cycle requires starting a cold engine and driving the vehicle until the engine reaches normal operating temperature. The next drive cycle doesn't begin until the engine has been shut off, allowed to cool back down and is restarted again.
On some vehicles, the drive cycle also includes the cold soak time between trips. On others, the EVAP monitor won't run unless the vehicle has sat for eight hours. There is no way to bypass or get around such requirements, so you have to do whatever the system requires. And if that means waiting, you have to wait.
READINESS ISSUES
One of the EPA's requirements for using a plug-in OBD II check in lieu of a tailpipe test is to make sure the OBD II system has run all of its monitors and that the monitors have all passed. But there's a catch. Some import vehicles have readiness issues when it comes to setting all the OBD II monitors. Consequently, the EPA currently allows up to two readiness monitors not to be set prior to testing 1996 to 2000 model-year vehicles, and one readiness monitor for 2001 to 2003 vehicles.
When OBD II runs a self-check on a particular component or system, it lets you know by setting a readiness "flag" or indicator, which can be displayed on your code reader or scan tool. If OBD II has run all the available monitors and all the monitors have passed (and no faults have been found) the vehicle should pass the OBD II plug-in test. But if all the required monitors have not run, the vehicle canno be given an OBD II test. The motorist must drive the vehicle and come back again, or take a tailpipe test if that is an option.
If OBD II detects a fault when running a monitor, the setting of a code may prevent the remaining monitors from running. A bad oxygen sensor, for example, will prevent the catalyst monitor from running. Getting all the monitors to run can be tricky on some vehicles. Each monitor has certain operating requirements that must take place before the self-check will run.
To set the converter monitor, for example, the vehicle may have to be driven a certain distance at a variety of different speeds. The requirements for the various monitors can vary considerably from one vehicle manufacturer to another, so there is no "universal" drive cycle that will guarantee all the monitors will be set and ready.
Mike Cole of the National Center for Vehicle Emissions Control and Safety (NCVECS) at Colorado State University says some vehicles require very specific drive cycles (called "drive traces" if you perform them on a road simulator or dyno) to activate certain self-checks like the catalyst and EVAP monitors. NCVECS has compiled all the known drive traces for various vehicles on a CD and offers the package to technicians for about $40. For more information, you can visit www.ncvecs.colostate.edu.
As a general rule, doing some stop-and-go driving around town at speeds up to about 30 mph, followed by five to seven minutes of steady 55 mph highway speed driving, will usually set most or all of the monitors. Consequently, if you are checking an OBD II system and discover that one or more of the monitors have not run, it may be necessary to drive the vehicle more to set the remaining monitors.
With the EVAP monitor, the vehicle may require a certain period of inactivity (such as sitting overnight) and certain ambient temperature conditions (such as above freezing) before the EVAP monitor will run.
Some vehicles with known readiness issues include 1996 to 1998 Mitsubishi cars (which require a very specific drive cycle), and 1996 Subarus and Volvo 850 Turbos (turning the key off clears all the readiness flags, so don't turn the vehicle off after driving). On 1997 Toyota Tercels and Paseos, the readiness flag for the EVAP monitor never will set, and no dealer fix is yet available. Other vehicles that often have a "not ready" condition for the EVAP and catalytic converter monitors include 1996-1998 Volvos, 1996-1998 Saabs and the 1996-1997 Nissan 2.0L 200SX.
DRIVE CYCLES
If the MIL comes on while driving, or remains on after starting the engine, it means OBD II has detected a problem. The lamp will usually remain on, unless the fault does not reoccur in three consecutive drive cycles that encounter the same operating conditions, or the fault is not detected for another 40 drive cycles. If OBD II sees no further evidence of the problem, it will turn off the MIL and erase the code.
An OBD II drive cycle is not just turning the ignition key on and off or starting the engine. A drive cycle requires starting a cold engine and driving the vehicle until the engine reaches normal operating temperature. The next drive cycle doesn't begin until the engine has been shut off, allowed to cool back down and is restarted again.
On some vehicles, the drive cycle also includes the cold soak time between trips. On others, the EVAP monitor won't run unless the vehicle has sat for eight hours. There is no way to bypass or get around such requirements, so you have to do whatever the system requires. And if that means waiting, you have to wait.
09-05-2008, 03:56 PM
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Drive cycles
I would think that 2 weeks of driving 50 miles to and from work would complete the requisite drive cycles. Being that I live in a state that will not issue a waiver, how can I drive on an uninspected vehicle. One $250 ticket for failure to inspect is enough.
I have used 2 different ECM's and nothing seems to work. If the ECM senses a fault, will it stay in the test mode? I have a code of p0161, which is the heater circuit for the aft cat o2 sensor, right side. But it's only pending, it hasn't set the code yet.
Thanks for everything,
Bill
I have used 2 different ECM's and nothing seems to work. If the ECM senses a fault, will it stay in the test mode? I have a code of p0161, which is the heater circuit for the aft cat o2 sensor, right side. But it's only pending, it hasn't set the code yet.
Thanks for everything,
Bill
09-05-2008, 10:32 PM
#5
I would think that 2 weeks of driving 50 miles to and from work would complete the requisite drive cycles. Being that I live in a state that will not issue a waiver, how can I drive on an uninspected vehicle. One $250 ticket for failure to inspect is enough.
I have used 2 different ECM's and nothing seems to work. If the ECM senses a fault, will it stay in the test mode? I have a code of p0161, which is the heater circuit for the aft cat o2 sensor, right side. But it's only pending, it hasn't set the code yet.
Thanks for everything,
Bill
I have used 2 different ECM's and nothing seems to work. If the ECM senses a fault, will it stay in the test mode? I have a code of p0161, which is the heater circuit for the aft cat o2 sensor, right side. But it's only pending, it hasn't set the code yet.
Thanks for everything,
Bill
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