Cel Code 71 Intermittent

[DanW]

This has been happening for a while now and its getting annoying.

I have been getting code 71 (EGR malfunction) intermittently for the last couple months. Usually when I fill up with gas, the CEL will go off after about 50 miles, then come one maybe 50-100 miles later. I think it's been on/off about 5-6 times by now.

Car runs/drives fine, gas mileage isn't affected.... I'm thinking the egr temp sensor itself may be acting up, or the vaccuum modulator might be getting clogged? Dunno why filling up with gas would make any difference to either of those.

Since it runs fine, I have largely forgotten about it for the last 1000 miles or so, but just lately its getting on my nerves!

Anyone have a similar experience?

[leximus]

I have the same exact issues. the egr temp sensor itself may be acting up, or the vaccuum modulator might be getting clogged, but I do notice that most times when I "open her up" on the highway, the CEL goes off for about 60-100 miles then goes back on again shortly thereafter. A mechanic I know who is familiar with my car says the same thing you're saying about "the egr temp sensor itself may be acting up, or the vaccuum modulator might be getting clogged". He says if I don't get it diagnosed/worked on soon, that my O2 sensors may need to get changed (again). It bothers me to no end also. I don't have money for the parts, but I do have a mechanic that will come to my house, diagnose and fix the issue.

[DanW]

I have the same exact issues. the egr temp sensor itself may be acting up, or the vaccuum modulator might be getting clogged, but I do notice that most times when I "open her up" on the highway, the CEL goes off for about 60-100 miles then goes back on again shortly thereafter. A mechanic I know who is familiar with my car says the same thing you're saying about "the egr temp sensor itself may be acting up, or the vaccuum modulator might be getting clogged". He says if I don't get it diagnosed/worked on soon, that my O2 sensors may need to get changed (again). It bothers me to no end also. I don't have money for the parts, but I do have a mechanic that will come to my house, diagnose and fix the issue.

Have you noticed any effect on your gas mileage or anything like that? I certainly haven't...it just doesn't seem to run any differently than it ever did. Its gone on and off a couple times since I posted that...definetely getting annoying but seems to run fine.

[leximus]

I have the same exact issues. the egr temp sensor itself may be acting up, or the vaccuum modulator might be getting clogged, but I do notice that most times when I "open her up" on the highway, the CEL goes off for about 60-100 miles then goes back on again shortly thereafter. A mechanic I know who is familiar with my car says the same thing you're saying about "the egr temp sensor itself may be acting up, or the vaccuum modulator might be getting clogged". He says if I don't get it diagnosed/worked on soon, that my O2 sensors may need to get changed (again). It bothers me to no end also. I don't have money for the parts, but I do have a mechanic that will come to my house, diagnose and fix the issue.

Have you noticed any effect on your gas mileage or anything like that? I certainly haven't...it just doesn't seem to run any differently than it ever did. Its gone on and off a couple times since I posted that...definetely getting annoying but seems to run fine.

Slight affect on the gas mileage. I'm just worried about replacing the O2 sensors AGAIN and then the EGR stuff...might as well get it done though...

[DanW]

For anyone else who is having the same symptoms, I finally got around to caring about this. Everything I could gather suggested the EGR vaccum modulator failing caused this intermittent CEL and code 71, with the CEL eventually coming on for good.

Amonth or so ago I took the vaccum modulator out and soaked it in seafoam for a few hours. Let it dry overnight. Pulled the EFI fuse to turn the CEL off. The CEL came back on almost immediately, code 71, and it never went off again for over 1000 miles!! Trying to clean it actually seemed to make it worse.

Then I was on vacation for 2 weeks and sort of didn't care.

Last week I replaced the vaccuum modulator (cost about $70 and takes about 5 minutes). I have had the car out for 3 drives and CEL has not come back on yet.

I took apart the old VM and it was all cruddy and the spring was corroded bad. The new one felt much more 'springy' when I tapped it on a table.

Hope that helps.

[ko90ls]

Strange thing is that the code 71 only appears on Calif. Spec LS400's. may or may not be a large issue since CA has some of the strictest emission laws in the nation. but the book says:

1)Check For Air Leakage in EGR system

2)Check EGR Vacuum Modulator

3)Check VSV with engine cold; Check VSV and EGR vacuum mod w/ engine warm

4)Check EGR valve

5)Check VSV for EGR

6)Check voltage between terminal EGR of engine & ECT ECU connector and body ground

7)Check harness and connector between engine & ECT ECU and VSV for EGR, VSV for EGR and EFI main relay

8)Check EGR gas temp sensor

Here's the info on the Calif Car:

51 ................. NA (4) ..................... Switch Condition

52 ................. On (1) ................... No. 1 Knock Sensor

53 ................. On (1) ........................ Knock Control

55 ................. On (1) ................... No. 2 Knock Sensor

71 (6) ............. On (2) ............... EGR System Malfunction

(California Only)

(1) - If vehicle is in test mode, diagnosis would not be

performed on this item.

(2) - If vehicle is in test mode, CHECK engine light would be on.

(3) - Electronically Controlled Transmission (ECT).

(4) - If vehicle is in test mode, CHECK engine light would be off.

(5) - High Altitude Compensator (HAC) sensor.

(6) - California vehicles only.

email or PM me for the details or more info (if available)

[DanW]

That's interesting....according to carfax this car began its life in california. I didn't know code 71 was only a CA thing....these days most places are a lot stricter on emissions than they were in 92, so in a way its probably nice to know when the egr is malfunctioning....Denver is getting pretty tough on the issue.