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3 Posts
Discussion Starter · #1 ·

New member--

Have a 99 astrao AWD with 4.3l engine--- 152k miles.
just recently started getting a P0147 code with my scanner. Cleared code but keeps coming back.
Internet says P0147 is oxygen sensor.
How many oxygen sensors does 99 astro with 4.3l engine have and exactly where are they?
Do I have to take the doghouse off to get at the oxygen sensor(s)?
Can anyone post a pictoral diagram of oxygen sensors and wiring connections.?
Any other advice for trouble shooting?
Engine runs fine with DTC P0147 showing but I suspect my gas mileage is suffering.



· Registered
2,641 Posts
Hi omsrof

Welcome to the Forum.

DTC P0147:
-HO2 Sensor fault. Incorrect reading or no reading to the VCM.
-Bank-1 Sensor-3 located after the cat and before the muffler.

Possible Causes:

-Bad Connection
-Worn or broken wires to that sensor
-Sensor Failure (most common Cause)

Hope this helps. Please keep us updated, Thanks.:)

· Registered
3 Posts
Discussion Starter · #3 ·
Thanks for the very prompt reply and the nformation.

I guess this means the 99 Astro has only one oxy sensor where you indicated?

I will get under the van to check it now that I know where it is supposed to be located.

Do you know where the wiring from the o2 sensor gets plugged into the wiring harnes to go to comouter (ECM?)
is the connector to harness up inside the doghoaus so that needs to be taken off.?

I have 2 Astro Vans now 96 RWD with 130k+ mi and 99 AWD with 152K+ miles. I've had these both since they were about 2 years old and have been very satisfied with their performance and capacity. The haul a ton of "stuff" and usually are reliable. Of course as the years go on they is stuff to replace. I really have no clue as to whether the Astros were high or low on reliabilty compaared to other vans but I have always like their capacity for their short length. The original Astro we had was a 86- the 2nd year of producetion and it also served us well. They never had great gas mileage because of their 4.3 l engine but I was always impressed with the reliabilit of that engin and to this day neither engine burns a drop pf oil but hen I have always replaced oil every 3 or 4K mi.

I was dissapointed when GM discontinued the mode las I would have bought another and didn't care for the replacements offered. It would have been nice if the Astro had been updated with dual sliding doors. I think their Dutch door idear that is on my 99 is a great idea.

I now also have a 2005 Chrysler Town and Country with Stow and Go seats that fold into floor and 2 sliding doors. That is great because it means I don't have to wrestle the seats out to carry cargo-- tough with Astro's since I am 75 now. The T&C has about 45K mi and I bought at about 35K so I don't have much info about reliabilty except Consumer reports. I rides more like a car and gets much better gas mileage ( 25mpg on road ) with it's 3.3l engine. I haven't done any work on T&C yet so don't know how easy it is to rok on but I know that the Astros with the doghouse etc are a bear to even change plugs.

Before I bought the T& C I was signed up for DIY ALLDATA website for astros which was pretty good for info about repair info but that is expired now and have signed up for T&C instead with ALLDATA.

I just found the asto/safari website last night and look forward to contributing some of my experiences that may help others.

I am impressed that some one responded to my question about oxy sensor in such a short time.

Thanks ,


· Registered
2,641 Posts
Hi omsrof

Actually you have 4 O2 Sensors, I was just replying to that particular code you posted. The plug-in for that sensor is located on the body support rib just above and to the left of it. You might want to check the plug-in first to see if it is making a good connection or not, it does happen from time to time (bad connection). My best advice here if your going to try to replace this yourself, is to buy an O2 sensor socket to remove it.

They can be very difficult to remove at times. If you can get a source of heat to apply to the exhaust pipe and a can of lubricant, then just work the sensor out slowly. It will more than likely just come out about a half a turn then stop. When that happens don't try to force it any further, just spray some lubricant on the threads and turn it back in, then try to remove it again. This will take about 5 or 6 times doing this procedure before it actually comes out.

As for the Astro/Safari reliability, I think they are very reliable overall. It's just how each owner drives them and maintains them that really plays an important roll in dependability. Gas mileage can be very good with these vans if you keep your foot out of it and everything relating to gas mileage is maintained and adjusted regularly (tire pressure, wheel alignment, etc.). I get 26-28 hwy now with the bigger tires on and different gear ratio, but I use to get 30-32 hwy with mine (really), easy driving of course . People don't believe it when I tell them this, but hey, I don't really care, I'm saving the money, not them,hehe.

A family member has a Dodge Caravan with the 3.3. You might want to have a look at the rear plugs if you think the 4.3s are hard to do, hehe. I like the Caravans seats (comfortable) and handling. I don't like the room or the nose heavy feel it has to it though. They do get up and go at bottom end (rpms), but top end has a lot to be desired. His has been very reliable to this point and he is very happy with it though and I guess that's what's important. You will never carry anywhere near the load these vans do with the front wheel drive uni-body set-up and they do struggle when you have 3 or 4 passengers in them as well, but this applies to any front wheel drive van.

All Data is very good and what a lot of the shops use as a reference for repairs.

This site is mainly based on sharing each others experiences to help each other out and look forward to yours.:)

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3 Posts
Discussion Starter · #5 ·
and thanks again for the info.

I guess there probably is a different code then for each of the 4 O2 sensors.
Can I get at the one sensor for code P0147 from underneath or need to take doghouse off.?

I didn't get under today to look for theO2 sensor because I was busy working switching a motor over from a old bass boat to a new ( for me ) pontoon boat without a motor and starting checking electrical. Luckily the controls on the pontoon are OMC like the motor so not much of a problem.

Regarding the T&C-- I know what you mean about nose heavy . Also the steering gear ratio is a lot higher and turning circle of the T&C is a lot greater than the Astro. I still am underestimating in parking and making sharp turns and get behind the curve and swing wide. Oh well- can't have everything.

The one thing I might mention that may be of help is my experience I had with error codes on my 96 Astro a couple of years ago. You might save this in your memory bank for future use if someone has similar problems.

I was getting a lot of error codes- randomly TPC, EGR and others and car would run like s#$t, poor idle and surging at idle and low gas mileage then it would go away and then come back. I had it in a Chevy shop several times- they wanted to start replacing things to see what would work because they coudn't figure out the exact cause because it was random. One thing a tech did mention to me on one of the visits was that the 5v reference voltage was fluctuating between 5V and 0 at various times so they had the idea I might have to replace the computer ( ECM ). I told them no to all that becuase of the cost.
Another suggesting from online was to take all the connectors out of the ECM and WD40 them and blow out with compressed air. I did that with no changes in performance. I also changed plugs, rotor and rotor cap with no joy in performance.
Anyway- on one of my trips on the hughway I had my scanner hooked up and i noticed that some of the sensor parameters ( TPS, spark advance etc would change randomly when I was cruising at highway spped and constant throttle setting. The values would change randomly - lik TPS would go to 0 and then back to some other steady value. I got to thinking about it and thought that with the varying sensor inputs to ECM the comouter was probably truing to constantly adjust to sensor indication of changing conditions when conditions were really not changing. So I got on All data and pulled up the circuit digagram for power train control and started looking at it. It finally struck me that alll of this could be due to a problem with the quality of the ground. I found that there were 2 separate grounds for different engine control circuits to the ECM but they were physically at the same place. These 2 grounds were heavy duty spade connectors that were atttached to the back of the engine block with about a 1/4" bolt ,just below the floor level when I took the doghouse off and near the center. I didn't want to back the bolt all the way out because it was difficult to grip the bolt to keep it from falling down below. So i just backed off the bolt enough so i could twist the spade connectors for the 2 grounds and twisted them back an fortha few times with the star lock nut nearly tight to scratch through any rust or grease and then tightend the bolt down again. Amazingly this solve all my random intermittant problems. It happened once again a few months down the road and I did the same procedure again and haven't had a problem since-- problem solved!!. So- logically a poor ground will keep the ECM getting random , intermittant and incorrect signals which drives it crazy trying to adjust fuel injection, timing etc. and results in poor performance, idling and poor gas mileage.
I went through all this because all my agony may be of use to someone else to solve seemingly intermittant rando problems and codes. I am not famiiar enough with the posting board to know hwere to post such information for others use so I thought I would tell you and you could have it in reserve if you see someone posting with similar problems.

I hope this helps someone else.

BTW -- i sure wish i clould get any wher near the gas mileage you get. I used to get somewher around 22- 23 mpg on long steady trips but now seems more like 18- 19 mpg. I put part of this down to the common practice of putting up to 10% ethanol in gas mixtures now. I think ethanol has about 2/3 the energy content of gasoline so i'm sure that has some effect.

Anyway-- thanks for you help on the O2 thing and I will post when work on it to see if I can solve that problem.

Do faulty O2 sensors affect gas mileage? I would think they would.

Just for reference for the future, can you tell me the specific DTC codes for the other three O2 sensors are also and where they are located?

Thanks again,


· Registered
2,641 Posts
Hi Omsrof

That's great information to know and thanks, I'm sure others will benefit from it. You access that sensor from underneath the vehicle. The one thing I would suggest not to do, is to spray the WD40 "into" the ECM,and not to blow things out with compressed air.

I would suggest and do this myself, is to only use Die-Electric grease on the plug-ins and use a vacuum of some sort to clean out the computer ports. WD40 is great stuff to spray on wires and the outside of plug-ins, I use it all the time on my vehicle.

As for gas mileage, yes I get that now (easy driving, hwy). Just to clarify here, is that I'm in Canada and the Imperial gallon is a bit larger than the US gallon and my mileage will always be a bit higher than the US vehicles.

4- Liters= 1 US gallon
4.54- Liters= 1 Imperial gallon
(Just to clarify)

Faulty sensors do affect gas mileage for sure. As for posting all the P codes for the sensors and their explanations to what bank or sensor, I can't do (just to many), sorry. But I can post the codes that cover the sensors.

Sensor P Codes: 1996 Astro/Safari

I hope this helps, and again thanks very much for that information you posted, very helpful.:)
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