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Discussion Starter · #1 ·
I have a CEL on and a slight misfire, the CEL goes off once and a while but comes on again shortly thereafter. I have brought it to 2 garages to get codes read (No Isuzu dealer anywhere near me, 800kms). Isuzu is like some rare unicorn around these parts and it scares the service guys to even look at it.

Anyway the first place I brought it to they told me it was a vaccuum hose off the throttle body, which he plugged back in and cleared the codes. Sure enough when i drove out of the parking lot the CEL was still there.

Second place I bring the truck to apparently has the most up to date OBDII software in town and tells me that it is showing "P1220 MFR Controlled fuel and air metering". To me this sounds like an O2 sensor or Mass Air Flow Sensor. Any thoughts??? Any insights on how I could furthur diagnose this?

I have 90,000kms (~56,000 miles) on the rodeo... I recently replaced the plugs (1 month ago) and have already had the IMG replaced.
 

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I HAD SOME OF THE ISUZU TECHS AT THE DEALER I WORK FOR CHECK AND THEY FOUND YOUR CODE P1220 UNDER 2001 RODEO SPORT AS A THROTTLE POSITION SENSOR 2 CUIRUIT FAILURE. THE ISUZU PART NUMER IS 8-97254-681-0; RETAIL PRICE $71.12. IF YOU WANT TO RDER THE PART YOU CAN CALL ME AT 503.292.8801 X340. I HOPE THIS WAS THE ANSWER YOU WERE LOOKING FOR, AND HOLD ON TO THAT UNICORN! :D
 

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The 2000+ 3.2/3.5 uses a throttle by wire system. No cable/direct link between the the go pedal and the throttle shaft. You do hear occationally of the TPS going bad. I think it's mounted somewhere on the gas pedal linkage. www.stcharlesauto.com would be another good source.
G/luck
Joel
 

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Discussion Starter · #4 ·
Well, i continued to drive the truck for another day, now i have it parked down at the shopping center and here I am at home. I start it now and the rpms jump around a bit then they jump to like 2500, and i get "reduced power" light on w/ CEL of course.

I gotta get it towed home now... Im going to go ahead and order the TPS from the nearest dealer since i need it fixed ASAP and cant wait too long for shipping. I have to wait till monday to order it because the service shop is closed for the weekend. If anyone else has anything to add before i order a new TPS let me know...

I had the TPS in my eclipse go about a year ago and tested it as described in this howto

http://www.geocities.com/MotorCity/Downs/7678/dsmtests.html#TPS

is this something that I could do on the rodeo to test the TPS? thanks
 

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I dunno if that testing procedure will work as those vehicles still have an actual throttle cable. You loose all accelerator pedal input on TBW equipped vehicles if you loose the TPS or servo motor that actuates the throttle. Is that what yours is doing? Does anything happen when you press the gas pedal? I don't see the advantage of TBW on passenger vehicles :( . I know it works well on OTR trucks, busses and construction equipment as running a cable is not practial on those. Hopefully that TPS is an easy r/r and fixes your problem.

G/luck
Joel
 

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Discussion Starter · #6 ·
yeah thats exactly what is happening... erratic idle with zero throttle response. Thanks for the help... i'll let you know how it goes in a few days
 

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Discussion Starter · #7 ·
I hate to be a pain, but i dont want to start ordering parts without being positive what the problem is. I came across a similar issue on 4x4wire from Stefano (who also posted this problem on here). Turned out it was a bad O2 sensor.

http://www.4x4wire.com/forums/showf...63771&page=0&view=collapsed&sb=5&o=14&fpart=1

When i had my IMG replaced the dealer told me I had an O2 sensor that was reacting slowly (that was 6 months ago). Could this be my problem? A faulty O2 sensor?
 

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You'd normally still have throttle control with a bad o2 sensor. Besides, Isuzu has had a few problems with DBW systems, so it's not like it's so uncommon for it to go. I'd check with St. Charles Isuzu as you get a discount plus free shipping. You could probably get them to overnight the part w/ some $$ and if they had it in stock. Also might want to try a Honda dealer if there's one local to ya. Just tell 'em you have a Passport.
 

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Discussion Starter · #9 ·
well its been well over a month since this issue with the rodeo came up... I have had it in to see a few different mechanics, but the best they could do is trial and error they say... which could have cost a bunch of $$$.

I had the wiring harness checked, and with correspondence from a isuzu dealer they were able to rule out the Accelerator pedal position sensor and the throttle position sensor. The next most likely suspect they say was the "fuel tank pressure sensor". Since this was a cheap part to replace i said "go for it" they replaced it over a week ago and the truck has been running as good as ever... Im sure glad its fixed, but its not at all related to the code pulled from the OBDII...

Thanks for all the help!
 

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Discussion Starter · #11 ·
I sold the vehicle a few years ago, but yes this was the problem...

The sensor is located in the fuel tank if I recall correctly. I'm sure if you Google it and or look in the shop manual you can find out more info about it.
 

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Buster28 said:
DTC P1220 is Throttle Position Sensor (TPS) # 2 fault.
Just to get back to a baseline, I reinstalled the old original TPS. The motor started and runs fast and pulsed with a little backfire in between at about 2500 rpm. The P 1220 TPS circuit 2 fault code came up and there are no other codes now. Where does circuit 2 go? Do you suppose it is still a faulty TPS and I should try a third one? I just hate to give up on the ole Trooper. Steve
 

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SteveSample said:
Buster28 said:
DTC P1220 is Throttle Position Sensor (TPS) # 2 fault.
Just to get back to a baseline, I reinstalled the old original TPS. The motor started and runs fast and pulsed with a little backfire in between at about 2500 rpm. The P 1220 TPS circuit 2 fault code came up and there are no other codes now. Where does circuit 2 go? Do you suppose it is still a faulty TPS and I should try a third one? I just hate to give up on the ole Trooper. Steve
I had a P1220 problem with my 02 Rodeo and it was caused by an intermittent open circuit in the 5 Vdc return ("ground") wiring for TPS#2. The copper conductor was broken inside the insulation because the wiring harness between the throttle body and PCM was made in such a way that it stretched the copper conductor causing an intermittent open circuit which caused the DTC P1220 to be set and the Reduced Power lamp to be illuminated intermittently. 00-02 Rodeo and Trooper throttle body wiring is identical.
Click image to expand,
 

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Again a million thanks. Would that be the the GRN/WHT wire? Steve
 

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The Green/White wire was causing the problem with my Rodeo but an open circuit in other two wires will also cause TPS#2 to quit working correctly. I localized the problem by shaking the wiring harness with the engine running at idle which caused the throttle valve to get twitchy and it was repeatable.
 

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Buster28 said:
The Green/White wire was causing the problem with my Rodeo but an open circuit in other two wires will also cause TPS#2 to quit working correctly. I localized the problem by shaking the wiring harness with the engine running at idle which caused the throttle valve to get twitchy and it was repeatable.
I'll give it a try. Steve
 

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Buster28 said:
The Green/White wire was causing the problem with my Rodeo but an open circuit in other two wires will also cause TPS#2 to quit working correctly. I localized the problem by shaking the wiring harness with the engine running at idle which caused the throttle valve to get twitchy and it was repeatable.
Eureka! I cleared the DTC codes and started the engine, which began to immediately rev to about 3000 rpm. Then I shook the harness in the two places that were somewhat loose; where the TPS harness curves and connects into the big bundle that goes back beside the passenger side valve cover and then at the back connection bundle where the wires angle and enter the Engine/Powertrain module on top of the passenger side wheel well. This also shook the computer connections that are covered by grey clip type covers. In a few seconds this gradually slowed down the high idle to 1000 rpm. It seemed that the computer was adjusting itself? I then ran the shift lever through the gear selections and the engine jumped up to 2000 rpm in each gear. After a few times doing the gear selections, the motor slowed down to the 1000 idle and dropped to a drive-able 500 rpm idle in sitting gears. Again, was the computer getting adjusted to the better inputs? No DTC codes came up in the next three cycles of start up! I will test drive it tonight when the wife can rescue me if things again go bad?

My question is now how and where do I begin replacing the evidently bad wires? Do I strip the tape wrap and splice in new wires for the TPS2 wiring diagram that Buster posted? These would be the GRN?WHT, Red/WHT and BLU/WHT from the last 1220 DTC code indications? OR is it possible and preferred to buy a new wiring harness, if it it even available? As ever, thanks. Steve
 

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Before tearing anything apart remove the 8 pin Throttle Body Harness connector E-5 and run some tests while manipulating the harness use a DMM with negative lead connected to negative battery terminal.
Click on image to expand
 

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Buster28 said:
Before tearing anything apart remove the 8 pin Throttle Body Harness connector E-5 and run some tests while manipulating the harness use a DMM with negative lead connected to negative battery terminal.
Click on image to expand
I cleared the codes and started the engine. It immediately revved up to 2500 rpm and then settled down to the 1000 rpm and would go into drive/reverse with no surge of rpm. I restarted again and then a P 1120 -TPS 1 circuit fault code came with an engine check light. The diagram on P 1120 on page 6E-387 shows GRN as the sensor ground, BLU as signal input and RED/BLU as a 5V Ref.

I am wondering how I can rely on any test if the codes keep moving around on me? I fix the wires on the one code and then the others act up? Also, I can tell if the bad wires are at the computer side or the TPS side of the harness? I'm temped to shotgun it and put replacement splices at the TPS side of all of the wires after the bend and trust the plug in harness connector. Then if that doesn't fix it, go to the computer side and do the same? It seems that the TPS wire colors are going to all over the two sides of the computer input though, not just one area of contacts. I determined this by matching the codes on the wires (ie: green with two silver marks). I must admit that my eyes started glazing over as I looked at the tangle of wires going into the computer. Then I wonder if the computer is the real problem? How did you fix your Rodeo? Thanks, Steve
 
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