(help)code p1491

my check engine light came on. i took my car to autozone. they did a system check . they coouldn't tell me what the problem was. they gave
me a dealer code of p1491 and told me it was the auxiliary emmisions control. i have know idea what to do with this since i bought it used
could some one please help

The first thing you would want to do is tell us what year and model your car is.
It would also be helpful to know if it is a 4 or 6 cylinder.
Kind of hard to diagnose things without at least knowing that.

P1491 is a know code for the EGR clogging that Honda is aware of. The fix (on a V6)
is to remove the intake and drill a hole larger and insert a metal tube that extends
further into the intake to help prevent the blocking of the hole.

This applies to the following cars:

1998–00 Accord V6 – ALL
2001 Accord V6 – 4-door from VIN 1HGCG1...1A000001 thru 1HGCG1...1A058564
2001 Accord V6 – 2-door from VIN 1HGCG2...1A000001 thru 1HGCG2...1A023388

This is from Bulletin #99-085 from Honda ...

In some areas of the U.S., certain basic chemical
properties of gasoline (regardless of brand) may cause
the intake manifold EGR port to clog or the EGR valve
to fail. If this happens, the MIL comes on with a DTC
P0401 (insufficient EGR flow) or P1491 (insufficient
EGR lift) stored.

American Honda is extending the warranty on EGR
system problems in the affected vehicles to 8 years or
80,000 miles, whichever comes first. To be eligible for
coverage under this extended warranty, the MIL must
be on with one of the above DTCs stored. Install the
EGR pipe kit, and file a claim using the information in
this service bulletin.

It also applies to others, like the Odyssey etc, but I am going to assume that you have an Accord.

If your car has passed the 80,000 mile mark ... you can still get it
fixed by applying this kit to it .... you will just have to pay for it yourself.



my check engine light came on. i took my car to autozone. they did a system check . they coouldn't tell me what the problem was. they gave
me a dealer code of p1491 and told me it was the auxiliary emmisions control. i have know idea what to do with this since i bought it used
could some one please help

my car is a v4 96 accord
i appreciate the help

OK ...

That can also be addressed.

From Honda ...

Quick Check of EGR DTCs P0401 & P1491

If the MIL is on along with DTC P0401 (insufficient
EGR flow) or DTC P1491 (EGR system malfunction)
on a ’94–96 Accord or ’95–96 Odyssey, do these
checks:

1. From the PGM Tester freeze data display, check
the EGR VLS (exhaust gas recirculation valve lift
sensor) voltage.

For DTC P0401, if the EGR VLS reads more
than 3.0 V, clean (unclog) the EGR passages. If
it reads less, go to step 2.

For DTC P1491, if the EGR VLS reads more
than 2.0 V, replace the EGR valve. If it reads
less, go to step 2.

2. Disconnect the vacuum hose from the EGR valve,
and attach it to a vacuum gauge.

3. Backprobe the RED wire in the EGR control
solenoid valve connector, then start the engine,
and let it idle.

4. While watching the vacuum gauge, apply and
remove ground to the RED wire 10 times.
Does the gauge read 6 inches of vacuum within 1
second of grounding the RED wire?
YES – Go to step 5.
NO – Replace the EGR control solenoid valve,
and clear the DTC.

5. Remove the backprobe, and apply 6 inches of
vacuum to the EGR valve.
Does the EGR VLS reading go to 1.2 V and stay
there?
YES – Replace the EGR valve, and clear the
DTC.
NO – Do the troubleshooting for DTC P0401 or
DTC P1491 (see section 11 of the appropriate
S/M).



my car is a v4 96 accord
i appreciate the help

The 4 cylinders usually have carbon build up in the EGR ports too. The comer is on the intake right under the injectors/rail. The injectors need to come out and then you can unbolt the plate and clean the ports. Also replacing the egr valve would be a good idea to.

OK ...

That can also be addressed.

From Honda ...

Quick Check of EGR DTCs P0401 & P1491

If the MIL is on along with DTC P0401 (insufficient
EGR flow) or DTC P1491 (EGR system malfunction)
on a ’94–96 Accord or ’95–96 Odyssey, do these
checks:

1. From the PGM Tester freeze data display, check
the EGR VLS (exhaust gas recirculation valve lift
sensor) voltage.

For DTC P0401, if the EGR VLS reads more
than 3.0 V, clean (unclog) the EGR passages. If
it reads less, go to step 2.

For DTC P1491, if the EGR VLS reads more
than 2.0 V, replace the EGR valve. If it reads
less, go to step 2.

2. Disconnect the vacuum hose from the EGR valve,
and attach it to a vacuum gauge.

3. Backprobe the RED wire in the EGR control
solenoid valve connector, then start the engine,
and let it idle.

4. While watching the vacuum gauge, apply and
remove ground to the RED wire 10 times.
Does the gauge read 6 inches of vacuum within 1
second of grounding the RED wire?
YES – Go to step 5.
NO – Replace the EGR control solenoid valve,
and clear the DTC.

5. Remove the backprobe, and apply 6 inches of
vacuum to the EGR valve.
Does the EGR VLS reading go to 1.2 V and stay
there?
YES – Replace the EGR valve, and clear the
DTC.
NO – Do the troubleshooting for DTC P0401 or
DTC P1491 (see section 11 of the appropriate
S/M).



Ive been noticing alot of your posts seem to be cut and pasted from somewhere and alot of these people on here have know clue what a PGM tester or an HDS is and alot of the tests need them to check out crutial voltages and other readings but the simple mater is not alot of people can access these testers so the info is pretty much useless to them.

Ive been noticing alot of your posts seem to be cut and pasted from somewhere and alot of these people on here have know clue what a PGM tester or an HDS is and alot of the tests need them to check out crutial voltages and other readings but the simple mater is not alot of people can access these testers so the info is pretty much useless to them.

So what do you suggest? Should I just give them bogus information like some people on here?

I happen to be a Service Coordinator for a Honda dealership and I am trying to help them get the best information that they can.

The information I post on here from time to time is directly from Honda. Can't get any better than that.

Sorry if you think that I should not get so technical ... but ... unfortunately the cars of today are just that.

The days of the old points and condensors are gone.

what im saying is this. Step one says from the freeze data on the pgm tester...

Ok so nobody has a pgm tester so now what? Now someone will jump around to a step that may seem like they can perform but if they must the important info in step one they could be on there way on a wild goose chase. What im saying is that we can give people tips and of what it may be or as a tech i can give them advise on what i have come accross in the past and what is a known problem accompanying that code.

Basically just don't copy and paste pages from ISIS just to run up your post counter. Thats all. If you have usefull advise post it otherwise don't confuse people with info they can't use.

I had a whole response to you about this ... but you know what?

Not worth my time.

I apologize for trying to help ... I will move on.

These guys are all yours ... good luck.





what im saying is this. Step one says from the freeze data on the pgm tester...

Ok so nobody has a pgm tester so now what? Now someone will jump around to a step that may seem like they can perform but if they must the important info in step one they could be on there way on a wild goose chase. What im saying is that we can give people tips and of what it may be or as a tech i can give them advise on what i have come accross in the past and what is a known problem accompanying that code.

Basically just don't copy and paste pages from ISIS just to run up your post counter. Thats all. If you have usefull advise post it otherwise don't confuse people with info they can't use.

Both of you chill out. Your both correct. Who gives a damn about post counts, you both were trying to help...helpful info is never useless. So please continue to help others in any way you can, and quit the bickering.