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Isuzu Trooper Check Engine Light

I've got a 93 Isuzu Trooper that is giving me a check engine light intermittently in the morning. Again, this only happens in the morning and is intermittent. When the car idles, I get no check enging light. When I accelerate, the check engine light comes on. In the afternoon, when the day is warmer, the check engine light stays off. I took the car into the dealer and was told this was the EGR valve so I have removed and cleaned the valve but am still getting the same check engine indicator. I am going to try and replace the EGR valve but was wondering if anyone has seen this before and could offer some advice before I go through the trouble and expense.


  • Hi, here is what the manual says about the EGR, should be about same for either v6 engine. If you would like the chart, here is a link: oto/v./photo.jpg

    Hope this helps.

    1993 Isuzu Truck Trooper (4 Door) V6-3165cc 3.2L DOHC (6VD1)
    Vehicle Level Powertrain Management Emission Control Systems EGR Valve Testing and Inspection

    Testing and Inspection

    Warm engine to operating termperature (120°F / 60°C).

    Place finger on on EGR valve diaphragm and accelerate engine, diaphragm should move.
    Disconnect vacuum hose from EGR valve.
    Using a vacuum pump, apply 10" of vacuum to the valve. It should move and engine should run poorly or stall.
    If valve passes above test use CHART C-7A. If valve fails, replace valve.
  • Thank you atfdmike, I'll test the EGR valve using these steps and see what happens.
  • Same subject but different ingredients! (In the UK)I have a 2001 Isuzu Trooper 3.0L diesel automatic which overheated on me whilst towing my caravan in hilly country. I noticed it before any damage was done but not before the Check Engine light came on. Thereafter the light came on and off in a completely random fashion without any apparent effect on the engine, all the functions of which seemed normal. However during a visit to the main Isuzu dealer nearby I asked them to plug in their electronic analyser thing, and they told me the throttle body needed replacing (at a great cost). I have obtained a replacement throttle body (not new but said to be in good working order) and having fitted it I find that the light comes on when the engine is not under load, but instantly goes out when an accelerator load is placed on the engine. This suggests to me that one or other of the sensors on the throttle body is minutely out of adjustment - I noticed that both the sensors have slotted mounting holes - but I am not able to find anywhere where the functions of the two sensors are described nor the manner in which they should be adjusted. Even the people I spoke to at the main dealers did not seem to know!! Can anyone please help.
  • atfdmikeatfdmike Posts: 414
    Unfortunately, the diesel has not been available in the US, so little practical experience with it here. On the gas engines though, the TPS (throttle position sensor)and other sensors for air flow and idle are also there and some are adjustable and I would imagine the same is true for yours. I assume you have already checked the fuel (and water?) filters as equipped?
    The procedure usually includes the use of a digital voltmeter and is not technically challenging, but hopefully someone who has done it or has a diesel manual will see your post and respond. One guys opinion.
  • mbp1mbp1 Posts: 1
    In my 1998 Trooper S, I've been getting check engine light due to insufficient EGR flow every year since the past four years. I was told by a dealer that this could be because of my shorter and slower commute (15 miles at 35 mph the most). The dealer advised me to occasionally use higher octane fuel. I've been doing that but no relief. I cleaned the valve and the inlet pipe from the exhaust just recently and reset the codes. But the problem resurfaced in a month.
    Any suggestions on resolving this issue?
    Any suggestions on cleaning the outlet pipe that goes into air intake? I could not clean this pipe properly. Is there any way to clean without opening the air intake?

    Thanks very much in advance.
  • twlsnbystwlsnbys Posts: 1
    I have a 2000 Isuzu Trooper
    and the check engine light
    stays on, i had it check out
    and it was the EGR valve.
    How do you remove the old
    EGR valve and replace it
    with a new one? Please advise.
  • atfdmikeatfdmike Posts: 414
    Located on RH side of engine near rear. It has a wiring connector and two bolts that hold it in place. The only way to verify it is working is to use a Tech 2 and monitor it while running.
    There is a gasket between it and the manifold that you may need to replace if in removing the valve it is damaged. Your discretion.
    Original Isuzu part no is 8170961783
    Hope this helps
  • wlbrown9wlbrown9 Posts: 867
    Here is a link to the FAQs. Look at the section on EGR cleaning. Might might be able to remove and clean it, if not you can just replace it.
  • get po401 error replaced erg valve light went off took to get IM inspection came back on failed with same error drove it for about 50 miles light went off again stayed off for 2 days now back on same error took to mechanic has no clue hard to find Isuzu dealers in UT any ideas what else problem could be---mechanic says could be wiring from valve or the whole computer. Random on and off of the check engine light with always same p0401 code. Really fustrated :sick:
  • atfdmikeatfdmike Posts: 414
    Hi, welcome to the forum. I am not sure which engine you have, as I have the older 3.2, but I did a quick search for you and found the following. It is a pretty common problem, and if you can figure out the location on your engine and clean it (try carb cleaner first, I think) by flushing it and soaking it to loosen deposits, you could resolve the problem. HTH

    " The car will not idle correctly, is difficult to start and runs rough much of the time. My truck did not do any of that. I was also told that in many cases, the insufficient flow may be from carbon in the passageways to and from the EGR valve. After some closer looking with a flashlight in hand, I found a plug that has access to the line between the ERG and the cylinder intake. The plug is located below the EGR unit on the left hand side. You will need a set of hex keys to remove this plug. Once I had the plug removed, I had clear access to the horizontal passageway to the engine intake. I quick inspection did show quite a bit of carbon build up within. To clean the passageway, I broke out my gun cleaning kits and used the barrel brushes attached to a 12 inch section of rod. I believe that it was the .40 caliber brush that was the closest in size. I also used the generic carb cleaner in the process as well. This scrubbing did remove much more buildup than I imagined. I installed the plug back in it’s place and have not had a 401 so far. So I believe that possibly could have been the problem. "
  • atfdmikeatfdmike Posts: 414
    The fact that the mechanic did not try to sell you O2 sensors leads me to believe that maybe what you need is a good long high speed run on the freeway to burn some of the carbon deposits on the valves, etc. After doing so a couple times, clear the code and see if it comes back. Post your results. HTH
  • My check engine light came on Code P0171 system too lean. How can I correct this?
  • I am having this problem for a couple of months now.The trooper has a PO171 code. I already change the 4 o2 sensor, clean the egr and reset the ecu.the trooper has 100,000 miles on the odometer and it has the original catalytic converter.I do not know for sure if this has something to do with the codes,and when i stand behind the muffler i notice the smell of rich mixture instead of lean mixture.if there is a answer for this codes,do i have to do the same as the other post or do i have to do other things?
  • Hey, I have an 02 Trooper 3.0L Turbo and the check engine light keeps flashing when i do around 50mph- any ideas what this could mean??
  • brentb1brentb1 Posts: 18
    check your intake manifold gaskets for leaks.when the vehicle is cold start it up and spray brake clean/ether at the gaskets,if the idle raises they are leaking.let me know what happens.
  • Engine runs rough at idle, once you get it going it seems to run okay, check engine light and three trouble codes, P171, P174 and P303. Left bank lean, right bank lean and misfire on cylinder #3. Change #3 plug, also trouble code book said MAF sensor bad. It got to the point that the engine would run rough at idle then die. Of course it would start up but you have to keep the rpms up or it would die. I unpluged the MAF and it would not die, within 30 secondsof pluging MAF back in engine dies. Bought a new MAF, it no longer dies but still runs rough and still gets the three trouble codes. signed sealfrog
  • brentb1brentb1 Posts: 18
    your intake manifold gaskets are bad.replace them.only takes about 40 minutes and 32.00 from autozone.
  • rob_w1rob_w1 Posts: 2
    i have a 2001 trooper, rescently it started to idle rough. I took it to a shop and the codes read basically a tune up and O2 sensor, having 75000 miles i had them do one. the trooper ran better, but still idled rough and the light was flashing at or about 2500 rpm. i took advice from another blog and learned the intake gasket was shot. i changed it and the truck runs alot better, but the light still is on and flashes after 2500 rpm, and reads no codes. Any ideas?
  • brentb1brentb1 Posts: 18
    yep my guess was the intake gaskets also.not sure why the light would still be on and no codes.disconnect the battery for 15 minutes that should reset it.let me know what happens.should clear all codes.if light comes back on you have to have a code stored...keep me
  • rob_w1rob_w1 Posts: 2
    I disconnected the battery and the light went off until i drove. i noticed the light flashes when i accelerate, when i let off the gas, the light stays on. could there be no code since the reader is checking while at idle? Is it possibly a throttle position sensor?
  • atfdmikeatfdmike Posts: 414
    Why not just get the codes read at an autozone or other for free. Once you know the code, that should help direct your efforts. That said, my guess is that you have an EGR problem, either needs to be cleaned or the valve itself is sticking or solenoid is not working. Odds are it is the EGRpassage in manifold. One guys opinion.
  • grabber7grabber7 Posts: 5
    I have a 2002 Trooper, 85,000 miles. When I accelerate the check engine light flashes, when I let off of gas it goes away. Just a weeks prior to this problem I turned on my heater and my truck died. There were none of these problems until I changed the spark plugs and put a new battery in it a couple of weeks ago. The battery that was in it was too small. Would either of these changes cause these problems?
  • wlbrown9wlbrown9 Posts: 867
    Troopers are real picky about the plugs you install. Stay with those listed in your owner's manual. My 2000 LS came with the following listed for use. I used the Champion RC10PYP4 that matched what came from the factory:

    Manual lists:
  • grabber7grabber7 Posts: 5
    I'm having the same problem except the light goes off when i let off the gas. I have a 2002 LTD 4wd.
  • grabber7grabber7 Posts: 5
    Is it okay to clean EGR with carb cleaner?
  • I am sure you did not disconnect the battery properly. When you did this You erased all the E.E.R.O.M Electrically erasable read only memory. I would not be surprised If the computer needs to be "reflashed" or reprogramed or even worse you might have done physical damage to the computer. Maybe if your lucky the PCM Power Train Control Module will re learn Its programed instructions.
    How do you know the battery was to small? Make sure you did not put a larger battery then needed compare the old and new battery. Hopefully you put O.E Orgnial equipment spark plugs in the car. There is a lot more to batteries, spark plugs and even air filters Nowadays. Every thing is tied into each other and the computer. I would suggest taking this to a shop. Hopefully this helped.
  • cleaning the erg valve isnt going to do anything you need to replace it. Here how to check to see if it is working (mechanical valves only) Have the vehical running take your hand under the egr valve and push up on the plunger if the car stumbles your good to go if not new valve or check for kinks in vaccum hose
  • I'm betting on intake gaskets. It'll just keep getting worse until the thing barely runs. The OEM's are a hard plastic that gets brittle with age. The good news is they are easy to change. Fel-Pro makes one that is softer, with steel inserts to keep it from getting crushed. You should be able to change both sides in less than two hours.
  • icarus681icarus681 Posts: 2
    Hi! I, already take out the manifold,and clean it,i also check the computer,clean the egr,change the O2 sensors,injectors were cleaned too,a new gas filter, i cant remember what more and the problem still,thanks for your response.
  • I am trying to helpl my daughter fix her 94 trooper, v6 dohc 4x4 4 dr......she has all kind of trouble lights took it to schucks to borrow a code reader, first off, they tell me they dont have an adapter for Isuzu, but that Chevy/GMC should then the cashier and I go out, pop the hood and spend a good 20 minutes looking stupid....then another good 10 minutes IN the car looking ever dumber..........does any one know where the code read is hiding?
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