Long List of DTCs...Could Use Some Insight

Like the title states I have a laundry list of DTCs showing up. To make this easy I'll start with the problems I have noticed.

I bought the Truck used and I'm not sure what has been done to it before. However when I went to buy the vehicle I did an inspection and took my OBDII scanner with me and the only alerts that came up were related to the airbag system.

Over the last couple weeks I've noticed a little stuttering during acceleration, idle, and driving slowly through parking lots. It got worse, but no CEL. I ran my OBDII scanner and a long list of DTCs came up.

I'm gonna post the current DTCs first and then tell you what I've done:

Other DTCs have come and gone as well. The ones in bold are persistent.

P0300 Toyota Readiness Random Misfire Detected
P0171 Toyota Readiness System Too Lean (Bank 1)
P0172 Toyota Readiness System Too Rich (Bank 1)
P0174 Toyota Readiness System Too Lean (Bank 2)
P0175 Toyota Readiness System Too Rich (Bank 2)
P0037 Toyota Readiness HO2S Heater Control Circuit Low (Bank 1, Sensor 2)
P0038 Toyota Readiness HO2S Heater Control Circuit High (Bank 1, Sensor 2)
P0057 Toyota Readiness HO2S Heater Control Circuit Low (Bank 2, Sensor 2)
P0058 Toyota Readiness HO2S Heater Control Circuit High (Bank 2, Sensor 2)
P0100 Toyota Readiness Mass or Volume Air Flow Circuit
P0101 Toyota Readiness Mass or Volume Air Flow Circuit Range/Performance
P0102 Toyota Readiness Mass or Volume Air Flow Circuit Low Input
P0103 Toyota Readiness Mass or Volume Air Flow Circuit High Input
P0116 Toyota Readiness Engine Coolant Temperature Circuit Range Performance
P0120 Toyota Readiness Throttle/Pedal Position Sensor A Circuit
P0121 Toyota Readiness Throttle/Pedal Position Sensor A Circuit Range/Performance


What I've done and why:

Changed out all the spark plugs with OEM plugs. The old plugs were very worn down, but I didn't see any high deposits of carbon or any other junk on them. They looked old, but clean.

Cleaned the MAF sensor and ran tests on it with multimeter. When I pulled it out it wasn't very dirty, but I cleaned it anyway. The testing showed no issues. However it was hard to pin down any parameters to check against, since the FSM suggests using an OBDII reader to do the test.

Cleaned the throttle body. The TB was dirty. I have no idea how the MAF was so clean while the TB was so dirty. Now it looks like new.

Installed new air filter. Old one was done.

Had battery load tested. Battery came back with no issues. It's old, but it's still fine.

Replaced gas cap. Why not? Old one had a very dry, but not yet cracked gasket.

Replaced Thermostat and Radiator Fluid. Since I wasn't sure what had been done and I'm coming up 150k miles.

Checked for vacuum leaks. Visually inspected and sprayed starting fluid around. No Leaks that I could find.

And that's it so far. None of these have fixed the initial issues though. And before you say I shouldn't be throwing money at it like this, I don't know what the previous owner has done. I have the funds to do these repairs and knowledge to do most myself, so why not?

And now I come to you and pick your brains. I was thinking my next step would be to check the fuel pressure (quick note, I can't for the life of me figure out how to do this). But if anyone has any other suggestions I'm game.

More info on the truck:
2005 PreRunner Access Cab
V6 4.0 Automatic

Thanks in advance. I promise to keep this thread updated with my progress. Nothing worse than someone coming in getting help and then....nothing.

 

bad ground strap?

 

Are there multiple ground straps? I hope I'm not sounding lazy, but I can only find one, and the only FSM I have is electronic and I can't search it easily.

Or if you could point me in the right direction in the FSM.

 

I believe there are 5, hopefully someone here has more specifics on the locations. I've had grounding issues on a vehicle before, not a Tacoma though. My car either wouldn't run very well, or not at all. Mine was a cheap fix, just took several hours to hunt them down. Maybe a Google search will point to their locations? Good luck, keep us posted.

 

Thanks for the insight. I found a chart in the FSM that lists the grounding points within the engine bay. Gonna go through it tomorrow when it's cooler.

Unrelated, or highly-unlikely to be related. I think a U-joint/s are going bad. Was under the truck earlier and they aren't very pretty and I'm getting some of the tell-tale signs. Gotta look into it some more. I'm about 50 miles away from 150,000 and since PO didn't provide any info on previous repairs or maintenance I'm pretty sure any repairs I do are being done for the first time.

Like I said I'll keep you guys updated as I go along. And any other insight would be greatly appreciated.

 

This is a shot in the dark but have you tested the alternator? If voltage rectifier is not working properly you may get ac voltage on the output. I've seen that cause all kinds of crazy problems including some you have listed and even seen the transmission hold gears longer than it should be for it shifts. I also agree with the grounds issue. Many times when you get a laundry list of Dtc it's something as simple as voltage being present where it should be or the opposite.

 

You know I haven't tested it yet and I will add it to the list.

 

Good advice in this thread - with the grounds and alternator as mentioned. You can check AC ripple voltage with a simple AC voltmeter (DVOM set to AC voltage) across your battery posts with the engine running. Anything over .3V (300 mV) means you have a diode issue in your alternator.

 

You guys are awesome. I was just going to ask if you had tips for checking the alternator. Is there a secret way to check the grounding issue besides visual inspection (and a little tug on the wires)? The grounds all looked good to me, at least the ones I could find.

Side note, I replaced all the U-Joints tonight. Once I saw some videos of other people's issues I was convinced mine were bad. And they were. Usually I go OEM or better with my replacements, but I went the cheap route because I've spent a ton lately and got Duralast U Joints. They have the port to add grease which is a huge plus. If I have issues I'll start another thread on that.

The front and back U-Joints were the worst of the group. Each had at least one set of bearings that were literally dust. And all of the bearings were damaged from heat, you could smell the burn and see how brown some of the bearing turned.

Front U-Joint:

Middle:

Back: