The upstream oxygen sensors report to the ECM the condition of the exhaust gas and the ECM in return adjusts the richness of the fuel mixture. It appears that both of your upstream oxygen sensors have low voltage according to the last two codes you posted. This causes the fuel mixture to be too lean which is what the first code is indicating. Seeing as both are upstream oxygen sensors are having issues based on the ECM's standards and that you just replaced most of the exhaust system, I would guess that you accidentally switched the wiring to the upstream oxygen sensors, or that they aren't properly plugged in. My first step would be to check out the wiring going to each oxygen sensor and make sure the colors in the diagram correspond to how your wiring is. For reference (if it's an automatic, which it should be since you implied two catalytic converters)-- Bank 1 is the driver's side, Bank 2 is the passenger side. Sensor one is on each downpipe just under the manifold, Sensor 2 will be behind each cc.
99 Trooper Loses Power When Accelerating
Hey guys,
It's been a while since I've posted anything, but I've got one that has me stumped. My exhaust was rusting apart and so I ordered a new exhaust. While waiting for it, the truck shut down one day. I tested a few things and thought it was the fuel pump. Dropped the tank and found a plug in the pump that was cooked. Replaced the pump, put the tank back on. Got the exhaust, put it on and realized the aftermarket cc was rubbing on the driveshaft on passenger side. I thought it might get through the shield but it actually punctured the cc. I ordered a cc that I could turn at an angle and that seemed to work perfectly. I take off down the road with my new exhaust and new fuel pump and no power.
I have a fuel pressure gauge and when I turn the trooper to "ON", fuel pump energizes with 42lbs but slowly starts dropping. When it fires up, which it doesn't hesitate at all, it drops to about 35 and seems to stay there.
I don't know if it's normal to start tailing off when fuel pump starts? When i start driving, it takes off fine, but when I accelerate, it feels like there's a governor on the the motor. It will not take off. Does anyone know what I should be looking at? I don't know if I screwed something up with dropping the gas tank or if I should be looking for leaks in the exhaust? The codes I'm getting are p1171, p0137 and p0157.
Any ideas would be appreciated!!
It's been a while since I've posted anything, but I've got one that has me stumped. My exhaust was rusting apart and so I ordered a new exhaust. While waiting for it, the truck shut down one day. I tested a few things and thought it was the fuel pump. Dropped the tank and found a plug in the pump that was cooked. Replaced the pump, put the tank back on. Got the exhaust, put it on and realized the aftermarket cc was rubbing on the driveshaft on passenger side. I thought it might get through the shield but it actually punctured the cc. I ordered a cc that I could turn at an angle and that seemed to work perfectly. I take off down the road with my new exhaust and new fuel pump and no power.
I have a fuel pressure gauge and when I turn the trooper to "ON", fuel pump energizes with 42lbs but slowly starts dropping. When it fires up, which it doesn't hesitate at all, it drops to about 35 and seems to stay there.
I don't know if it's normal to start tailing off when fuel pump starts? When i start driving, it takes off fine, but when I accelerate, it feels like there's a governor on the the motor. It will not take off. Does anyone know what I should be looking at? I don't know if I screwed something up with dropping the gas tank or if I should be looking for leaks in the exhaust? The codes I'm getting are p1171, p0137 and p0157.
Any ideas would be appreciated!!
1 - 12 of 12 Posts
P1171 is a failure detected during a power enrichment test which indicates there is a fuel delivery problem. It is highly likely the O2 sensor issues are related to the fuel delivery problem. You may have a clogged fuel filter or defective fuel pressure regulator or defective fuel pump or water in the fuel.
DTC P0137 is HO2S Circuit Low Voltage Bank 1 Sensor 2
DTC P0157 is HO2S Circuit Low Voltage Bank 2 sensor 2
The Powertrain Control Module (PCM) supplies bias voltage of about 450 mV between the heated oxygen sensor (HO2S) signal high and signal low circuits. When measured with a 10 megohm impedance digital voltmeter, this may display as low as 350 mV. The oxygen sensor varies the voltage within a range of about 1000 mV when exhaust is rich, down through about 10 mV when the exhaust is lean. The PCM constantly monitors the HO2S signal during “closed loop” operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary.
If the Bank 1 HO2S 2 signal voltage remains excessively low for an extended period of time, DTC P0137 will be set.
If the Bank 2 HO2S 2 signal voltage remains excessively low for an extended period of time, DTC P0157 will be set
DTC P0137 is HO2S Circuit Low Voltage Bank 1 Sensor 2
DTC P0157 is HO2S Circuit Low Voltage Bank 2 sensor 2
The Powertrain Control Module (PCM) supplies bias voltage of about 450 mV between the heated oxygen sensor (HO2S) signal high and signal low circuits. When measured with a 10 megohm impedance digital voltmeter, this may display as low as 350 mV. The oxygen sensor varies the voltage within a range of about 1000 mV when exhaust is rich, down through about 10 mV when the exhaust is lean. The PCM constantly monitors the HO2S signal during “closed loop” operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary.
If the Bank 1 HO2S 2 signal voltage remains excessively low for an extended period of time, DTC P0137 will be set.
If the Bank 2 HO2S 2 signal voltage remains excessively low for an extended period of time, DTC P0157 will be set
Thanks Buster! I'm changing the fuel regulator in a few minutes. The hose was badly worn and snapped at the nipple on the block when I was changing it. Waiting for my wife with her toddler sized hands to get the inch of hose off of there. My big fat fingers can't get in there. I guess I'll start there.
Do you think it has anything to do with dropping the tank when I changed the pump? Maybe I didn't get the seal right? My fuel filter is brand new. I'll let you know on the pressure regulator. Thanks!! I'm glad you're still on here!
Do you think it has anything to do with dropping the tank when I changed the pump? Maybe I didn't get the seal right? My fuel filter is brand new. I'll let you know on the pressure regulator. Thanks!! I'm glad you're still on here!
Ok, took the trooper out and the fuel pressure regulator was a HUGE improvement. I would jump on the throttle at about 25 mph and it actually down shifted and took off. I was shocked! But, the downside...after about 4 miles, check engine came on. I'm now getting 0137, 0157, 0171 and 1171. I'm thinking I hear a leak on the drivers side exhaust manifold. I wish I had a smoke machine but I'll check for sure in a bit with some soapy water and if need be, I've got the drivers side manifold gasket that I can put on.
Am I barking up the right tree with those codes do you think?
Am I barking up the right tree with those codes do you think?
Connect a fuel pressure gauge to the fuel rail test port. Turn the ignition switch to Run for 15 seconds and back to Off with out cranking the engine. The expected result is the pressure remains close to 40psi for several minutes and very slowly bleeds down to zero. If the pressure drops quickly to zero there is a leak.
I'll do that as soon as I get home from work tonight-thank you!Connect a fuel pressure gauge to the fuel rail test port. Turn the ignition switch to Run for 15 seconds and back to Off with out cranking the engine. The expected result is the pressure remains close to 40psi for several minutes and very slowly bleeds down to zero. If the pressure drops quickly to zero there is a leak.
I put the fuel pressure gauge on the Trooper tonight. It only went up to 35. It tok 3 1/2 min to get down to 30, 5 min to 29, 7 min to 25 and 10 1/2min to get to 20. I'm confident that my #5 injector is leaking. There is fuel around it when I was doing the test. I could say #4 also, but it's right under the fuel rail port, so I'm not sure if that fuel is from my putting pressure tester fitting on or if it's in fact leaking. I tested all the injectors when I put new intake gaskets on, but I didn't put new o-rings on🤥so I really shouldn't be surprised. Is the fact that it only went to 35 concerning? Do you feel like that slow of a rate to drop is slow enough to rule out a leak?
Try the test again but have helper operate the key so you can observe the pressure as soon as the key is placed in the Run position. 35psi is lower than expected.
Today is the first day I'm going to be able to work on the Trooper. Waiting for my kid to get home to help me test the fuel pressure, so in the meantime, I'm looking for exhaust leaks. The passenger side exhaust manifold, brand new felpro gasket, and it's leaking badly. I've got the nuts all at spec(42ftlb) and even to get there, they feel like they're about to snap. How can I seal this manifold? Are there any little tricks? Or am I going to have to pull it AGAIN and put new studs in or completely replace the manifold?
1 - 12 of 12 Posts
Isuzu SUV Forum
A forum community dedicated to Isuzu SUV owners and enthusiasts. Come join the discussion about performance, modifications, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
