3.4L OBDII code deciphering help

January 23rd, 2011

OK, I admit I am not a rocket scientist when it comes to the newer electronic EFI junk, but I think I can even recognize bad news when I see it. Someone tell me differently...

So my rig has had a starting problem for awhile. I took the time to go through all of the electric junk from the batteries forward, cleaning off all the connectors, replacing grounds, etc., etc. all the way up to the the electronic stuff. While I was doing this, I also took the time to replace all the fuses and all the relays. It still didn't start, but not for lack of juice.

Next I decided to go through the whole fuel system, checking the fuel pump, replacing the filter, draining the tank, blowing out the fuel return line, etc. Now I have a handy dandy access panel cut through my truck bed for fuel pump access and know that the WalPro 190 fuel pump I stuck in there 6 years ago works like a charm..

Anyway, I was now down to the electronics...(did I mention I know dick about them?)..not to mention the fact that to get to the ECM and have at least a little room to work, I had to remove the seat, the speaker, half of the dash, the glove box, the heater motor, six years of under dash dust (tube doors half the year make for a nice mess. I was surprised that I didn't have moles living under the dash..)...you get the picture..

I decided today to go down to the local Checkers and make use of their rent a tool program. I grabbed an OBDII reader, sans instructions, hooked it up and the very first OBDII code I have ever read in my life was this one:

DTC P1600 ECM BATT Malfunction

A03375
Battery
2
R/B No. 2
E5
ECM
BATT
2
B–Y
15
IF1
W EFI
16
2
1
B–Y
DIAGNOSTICS – ENGINE (5VZ–FE)
DI–279
2002 TOYOTA TACOMA (RM921U)
DTC P1600 ECM BATT Malfunction
CIRCUIT DESCRIPTION
Battery positive voltage is supplied to terminal BATT of the ECM even when the ignition switch is OFF for
use by the DTC memory and air–fuel ratio adaptive control value memory, etc.
DTC No. DTC Detection Condition Trouble Area
P1600 Open in back up power source circuit
Open in back up power source circuit
ECM
HINT:
If DTC P1600 is displayed, the ECM does not store another DTC.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
Read freeze frame data using hand–held tester or OBD II scan tool, as freeze frame data records the engine
conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the
vehicle was running or stopped, the engine was warmed up or not, the air–fuel ratio was lean or rich, etc.
at the time of the malfunction.
DI0SG–15
A18845
BATT (+)
A18222
EFI Fuse
R/B No. 2
DI–280
DIAGNOSTICS – ENGINE (5VZ–FE)
2002 TOYOTA TACOMA (RM921U)
1 Check voltage between terminal BATT of ECM connector and body ground.
PREPARATION:
Remove the glove compartment (See page SF–58).
CHECK:
Measure the voltage between terminal BATT of the ECM connector
and the body ground.
OK:
Voltage: 9 – 14 V
OK Check and replace ECM (See page IN–28).
NG
2 Check EFI fuse.
PREPARATION:
Remove the EFI fuse from the R/B No. 2.
CHECK:
Check the continuity of the EFI fuse.
OK:
Continuity
NG Check for short in all harness and components
connected to EFI fuse.
OK
Check and repair harness or connector between
battery and EFI fuse, and EFI fuse and
ECM.

Me again...Since I replaced the EFI relay with a brand new Toyota unit and have power to the fuse box, then I am going to assume that that part is OK, as well as all the rest of the fuses and relays. I removed the connectors from the back of the ECM and there was corrosion(?) on some of them. I used a quality electronics parts cleaner to remove this on both the male and female parts, also removing the cover (hell, what did I have to lose at this point?) from the ECM and cleaned the board the same way I would do a regular computer MB. Let it dry, stuck dielectric grease on all the connectors, plugged the OBDII scanner back in, turned the key on and got the same code....Surprise, surprise, the rig didn't start then either...

So, being the non electronic wizard I am, I am assuming the this equates to the Windoze "Blue Screen of Death" and pretty much sounds the death knell for the ECM.

So, if there is anyone who knows OBDII codes and electronic EFI systems well, please speak up as I could use a little input before shelling out the big bucks for a new ECM...

Thanks in advance.

January 23rd, 2011

have you tried hitting it with a hammer?????

sorry- couldnt help it.
and im not that smart about the 3.4. sorry- i just posted to tell a joke.

January 23rd, 2011

Thought about shooting it with either the .44 or the 12 gauge, but then realized that I can shoot a computer anytime, so the fun went away.....I have a friend who is an IT tech and we shoot old laptops and HDs with large caliber weapons...Cheap therapy. Takes longer to pick up the pieces than it does to shoot them, though, which is the only drawback....

**Metalhed** · January 23rd, 2011

Pete what kind of starting problems, hard to start, rough running, start/no start, ???

If you followed the OBDI reader directions and checked all the voltages and connections. The only thing left is the ECM

Pulled this tidbit from another forum
"""After looking in FSM, P1600= ECM Battery Malfunction, what this means is you have no battery power to the ECM at the Batt terminal. There should be +12V at this terminal at all times even with the ignition off.

The first thing is to solve this problem, without the +12V at the Batt terminal the ECM will not store any other codes that may be showing, in other words you may have other problems that are not showing up on the scanner because the ECM is unable to store them because of the power loss to the Batt terminal.

The Batt terminal 12V power is also used by the air-fuel adaptive control value memory, which could be the cause of the ruff idle.

Check your EFI fuse first. """

The Dude fixed it, had an intake gasket leaking
I am still searching

Yotatech brings up some issues with the pins and wires. Did the ECM get bumped? did the wires short out or get detached?
P1600 keeps bringing up the need for constant power, for the 'puter to work

hope this helps

**Metalhed** · January 23rd, 2011

Looks like the ECM internal battery might have died? No way to replace other than new ECM

More searching still

Pete are you running a piggy back computer for the fuel trim or just the Toyota computer. Do you have Gadgets fuel add-ons for the supercharger? Split-Second, WideBand O2 sensor, full time lap top for trim....?
Maybe if you disconnected them and ran the Toyota computer alone it might start. Worth a shot.

January 24th, 2011

Looks like the ECM internal battery might have died? No way to replace other than new ECM

More searching still

Pete are you running a piggy back computer for the fuel trim or just the Toyota computer. Do you have Gadgets fuel add-ons for the supercharger? Split-Second, WideBand O2 sensor, full time lap top for trim....?
Maybe if you disconnected them and ran the Toyota computer alone it might start. Worth a shot.

Yeah, that is the impression I am getting.

As to the piggy backs, no I am not running one yet, just the WalPro190 pump and the bigger Bosch injectors. It is simply the stand alone Yota ECM.

And it is doing what the stuff you found said. I can't get past the very first P1600 code so everything just stops at the ECM..

As far as the starting:

It started acting like it was either flooding or not getting enough gas, finally draining the battery. Then it would start and, once warmed up, would run fine. Starting problems continued, whether hot or cold, engine warm or not, until it finally wouldn't start at all. I cleaned the TBI, IAC, and MAF, and replaced a bunch of vacuum lines at this point, then decided to go through the electrical system. Plenty of power, engine spins fine, power to the fuse panels, gas to the injector rail, etc., just no part B.

Thanks for the reply and helping with this!

**Brad** · January 24th, 2011

I have alot of experience with this, do you have the pinout sheet of the ECM?
If so have you checked the specific terminal for voltage?
Have you cracked open the ECM to check for internal corrosion?

**foxtrot** · January 24th, 2011

you could try borrowing someone elses ECM that has the same 3.4L and see if that will work. will tell you if it rules out the ecm

January 24th, 2011

I don't know anyone who does. Besides, it is both a royal pain to get to and to pull the plugs from it. I had to just about disassemble the whole damn dash to get access, including pulling the heater motor. I am certainly not going to bother someone to do that for me. Too much of a PITA.

Toyota will do the same thing for $200 bucks or so , minus the towing charges to get the truck there. They won't 'loan' out an ECM for testing. By the time I have this done by them, including towing charges to and from, I am out more than getting it rebuilt by about $100.

Thanks for the thought and reply, though. This is another 'fix it with no money' fix, so I have to be very careful of what I spend on it. After all, it isn't my DD I am working on, merely a 4x4 play toy.

**Brad** · January 24th, 2011

ColoDisco previously posted:

January 24th, 2011

I have alot of experience with this, do you have the pinout sheet of the ECM?
No, but I can locate one.

If so have you checked the specific terminal for voltage?
Going to do that now. Voltage reads 0000, so that pretty much indicates the ECM is shot.

Have you cracked open the ECM to check for internal corrosion?
There was some corrosion on the plug ins, but I cleaned that with electronic parts cleaner, both male and female, stuck some dielectric grease on the connectors, popped the cover on the ECM (which was dusty, but very clean) and cleaned that off like I would a regular computer MB. I then put the scanner back on and got the same P1600 code.

Sending it off right now to get rebuilt and R&R'd. Everything I found said that the tests I ran with the voltage and continuity results I pulled up, along with the no start and DTC code 1600, shows that it is a problem with the actual ECM itself.

**Brad** · January 24th, 2011

Did your ECM get submerged in water?

January 24th, 2011

Nope, but that isn't saying it didn't get wet, even buried under the dash. Half the year we run with just tube doors, so weather gets into the rig. When it gets reinstalled, more care will be taken as far as waterproofing goes. Have to keep in mind that is was a used ECM out of a used 1998 4Runner(the donor rig for the engine) , is now 13 years old and has been in my rig since I did the engine transplant 6 or more years ago. The rig has been soaking wet, inside and out and has also had a fair amount of snow in it at various times. The ECM was buried up under the dash and mounted quite a bit higher than the stock location. When I mounted it, I wrapped it in foam, then wrapped that in duct tape, so I thought it was good to go. The connections on the back were the only places where I found any corrosion anywhere on any of the connectors..

January 28th, 2011

Well, a brief update:

I sent the ECM off to ECM Depo who rebuild ECMs and just heard back from them today. The processor, which isn't replaceable on the Yota boards, is fried...as in non repairable. They were able to locate a rebuildable core and are going to get the rebuilt unit back to me sometime next week with the addition of a core charge. Total price is going to be around $350, which beats a new price of over $1100 hands down.

So for the first time use of an OBDII scanner, I sure pulled the "blue screen of death" code....and managed to do all the checks to make sure it wasn't working right. Glad to see that I wasn't wrong...

The guy I talked to said that it was nice that I had a Yota and not a Dodge as the Dodge ECMs have 1/3 to 1/2 the life span of any other makes. They said they do a bigger business in Dodge ECMs than any other make...something I sure didn't know.

**Chris** · January 28th, 2011

Brody previously posted:

January 28th, 2011

Well, it comes with a no question 1 year warranty and is supposed to be rebuilt up to factory specs, so probably longer than the engine is going to last....or at least another 11 or 12 years.

**Hypoid** · January 29th, 2011

Brody previously posted:

**Brad** · January 29th, 2011

I recommend cracking the case and putting in thin beads of silicone instead of wrapping it. Just like any computer they can get pretty hot. My ECM is behind my glove box as well and I worry if I get into deep water it will suffer the same fate. My plan is to seal it up then source a tcm box from a junkyard Audi and seal it in that then remount it.

January 29th, 2011

Maybe you should let the new one breathe?

I left the back part where the plugs go in free of tape and foam just for that reason.

February 15th, 2011

So, the processor was fried, the company had to order a different unit to be rebuilt. They called last week and said I should have it Friday. Great!, I thought. Good weather and can get it in and running, get Adam to help with the Split Second ECM install, etc. Friday, no go. Yesterday, no show. I called them this AM and it is in Kelso, WA. Now it is back on it's way to me. Here is the tracking information for a good grin. Keep in mind that this was shipped from Texas. Take a look at a map and see where it went for an even bigger laugh...

Kelso, WA, United States 02/15/2011 10:24 A.M. The Delivery Intercept request for this package was successfully completed. / The address has been corrected. The delivery has been rescheduled.
02/15/2011 8:12 A.M. The shipper has requested a Delivery Intercept for this package. / Delivery to an alternate address was requested.
02/15/2011 3:45 A.M. Arrival Scan
Portland, OR, United States 02/15/2011 12:32 A.M. Departure Scan
Portland, OR, United States 02/14/2011 12:25 P.M. Arrival Scan
Hermiston, OR, United States 02/14/2011 8:12 A.M. Departure Scan
02/14/2011 7:30 A.M. Arrival Scan
Salt Lake City, UT, United States 02/11/2011 4:33 P.M. Departure Scan
02/11/2011 12:52 P.M. Arrival Scan
Commerce City, CO, United States 02/11/2011 4:08 A.M. Departure Scan
Commerce City, CO, United States 02/10/2011 9:24 P.M. Arrival Scan
Dallas, TX, United States 02/09/2011 11:40 P.M. Departure Scan
02/09/2011 7:54 P.M. Origin Scan
United States 02/09/2011 10:19 A.M. Order Processed: Ready for UPS

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