CEL/DTC "Check Engine" Light, but no codes??? (1 Viewer)

[bamachem]

I'm at a loss.

Two days ago, the Hundy threw a code, ran a little rough, but not bad as I was pulling into my neighborhood.

Got home and parked it. Came back out a little later to see what it might be and the CEL was now gone.

Got in it and as soon as I gave it a little throttle in Drive, the CEL came on again, ran a touch rough, but really with a noticible reduction in power (but I don't think this is limp-home mode).

I pulled into an Advance Auto store this morning to pull the code. Nothing. Didn't show anything, even w/ the CEL currently lit on the dash.

Strange.

Got to work and borrowed a buddies ODBII.

Same thing. CEL on dash, but no current codes and none stored in history.

What's my next step? Dealer? Is there a way to jumper out the pins in the diagnostic connector to pull a code by counting the bulb flashes on the dash?

I've searched but can't find anything....

 

[bamachem]

VSC TRAC and VSC OFF lights are on now. Codes were P1300 and P1325. Cleared, pulled ECU fuse, and restarted truck. Immediately threw P1300 again. Off to dealer for $115 coil pack.

 

[NMuzj100]

You're in the Coilpack FAQ before you've even fixed the problem.

 

[bamachem]

OK, problem here.

First, the part number of the new coil pack did not match the part number for the original... Looked the same, but I'm questioning as to whether I got the right part. (I searched and verified that Mr. T did a part number upgrade for the original. I have the correct part.)

Original: 90919-02230

New: 90080-19027

Second, I replced the Number 1 coil pack (front, driver side), pulled the negative battery cable, and fired it up. No CEL for about 25 seconds, then it came right back. After a few more seconds, the VSC lights came back too.

Hmmmm... I'm thinking maybe Number 1 was good after all and number 6 was bad because of the P1325 code. I took the old Number 1 and put it in place of Number 6. Still had a CEL with VSC lights.

Drove to Advance Auto and pulled the code. P1300.

Cleared the code with the reader, took key out of the ignition for 10-seconds, then back in and cranked. CEL came back instantly, but no VSC lights. No code detected.

Drove home (2-miles) and still no VSC. Same symptoms - sluggish acceleration and overall funky feel to the engine.

So, the New coil is still at Number 1, the Old Number 1 is at Number 6, and I am not getting a Number 6 code (P1325).

Therefore the old Number 1 pack should be good, and there is another issue lingering.

Ideas? What's next?

 

[bamachem]

Checked and cleaned (with electrical contact cleaner) the injector plugs on 1 and 6. Pulled the new pack and put the old Number 6 back on 1. No changes.

Truck runs perfect for ~23-seconds. At that point, it has a slight stutter, idle drops, and CEL comes on. Idle jumps back to normal, but truck is in "limp-home" with reduced power and sucking the gas like crazy.

This is repeatable at this point...

However with just the CEL lit, there are no codes. Once the VSC lights are triggered, the code shows up.

 

[bamachem]

Here's a diagnostic procedure for P1300 P1305 P1310 P1315 P1320 P1325 P1330 and P1340.

PDF Diagnostic

Looks like since I had an intermittent P1325 with the P1300, there's a possibility it's just a connection issue, or a faulty ECM. Nice...

 

[bamachem]

OK, I went back out and pulled the new coil pack - while the truck was running - and you really couldn't tell a difference in the idle with #6 disconnected completely. I put the old coil pack back in, and made zero difference.

I shut things down, pulled the neg batt cable for a couple minutes and then started back up. Ran perfect for a while.

It idled high as it should when cranked somewhat cold and on a fresh ECU. As the ECU brought the idle back down, as it got to about 1k or so RPM, it hits a sumble, which triggers a CEL, but no VSC lights. That stumble at idle is what's causing me fits. I don't think I have a bad coil pack.

That means that I may have a faulty ECU. Wonderful.

I'm digging into it more and more now. Pulled all Coil Pack and Injector plugs and cleaned well with Contact Cleaner. Pulled IGF plug going to ECU and cleaned as well. Still does it. Inspected wiring for ANY signes of wear or overheating, and found none.

Pulled suspicious coil packs and associated plugs. Plugs looked OK, and tested fine when grounded and engine running - plenty of spark. Again, engine does not feel like it's missing, but it has that initial stumble, then it's in "limp-home" mode with a crazy fuel map, retarted timing, and low power.

Now I'm at the top of page 557 in the above link. I'll have to get a volt meter and check the signal coming off the harness to the ECU tomorrow. I'm done with it tonight. I'm hoping that I'm not looking at a ECU issue here...

 

[NMuzj100]

Sucks but it looks like you are going about it the right way.

More likely to be a harness or wiring problem than the ECU.

You might want to start tomorrow by replacing the EFI fuse under the hood. Others have had problems with ignition traced to the fuse even when they look good. There is a spare sitting in the top of the fuse box so it takes about 30 seconds.

 

[bamachem]

I think I have the issue narrowed down (in my mind anyway), but it's not going to be fun to find it.

I believe that I have some water in an electrical connection somewhere in the harness, causing a ground/short.

Thinking back, on the day this happened, I had washed out the engine bay with the water hose, but didn't drive it until later in the evening. By the time the code popped up, I had completely forgotten about the "rinse". Only reason I did it is because a couple days before I spilled a little ATF when refilling the pan. It was making for some funky smells, so I popped the hood and sprayed things off at the trans dipstick area. Well, looking again last night, there's a harness distribution box right there, and that's right where the Number 1 coil pack wiring goes.

My guess is that I got a little agressive on the water, it got up in a plug/clip or something, and that's what's triggering the intermittent short. At least that's what I'm hoping for. I'm going to pull things in that area apart today and hit them well with contact cleaner on an plugs, and probably heat them up with a hairdryer.

Crossing my fingers...

 

[bamachem]

OK, so all the original coil packs are in the truck, and it spent the night in the garage (warm) with the hood up to see if it helped with any moisture issues.

Cranked up this morning and no CEL. Hmmmm...

Drove AWESOME (I put some diaelectric grease on the injector and coil plugs when I was checking them) and had tons of power. Felt nice.

Hit it hard a few times with high RPMs and no issues for the first 8-10 minutes. Settled down and driving at a steady 60-MPH on back roads and the CEL came back.

Continued on to a local TM outlet and got my Zac Brown tickets. When I came out, the CEL was gone again. It returned within 5-min of driving.

It's having an instantaneous stutter that's triggering the CEL, but not throwing a code. The only time there's a code is when the VSC lights are on as well.

I'm about to go pull things apart and attempt to dry them out. Also going to look for any ATF that could have gotten on a connection and then dried on it, causing electrical disontinuity.

 

[AimCOtaco]

I'm about to go pull things apart and attempt to dry them out. Also going to look for any ATF that could have gotten on a connection and then dried on it, causing electrical disontinuity.

bamachem, At least you haven't thrown a bunch of money at the problem. I commend you for your systematic approach.... Given the improvement of the dry out day I really think your on it and will be fixed after a good clean up!

Good Luck!

 

[bamachem]

Here's a diagnostic procedure for P1300 P1305 P1310 P1315 P1320 P1325 P1330 and P1340.

PDF Diagnostic

Looks like since I had an intermittent P1325 with the P1300, there's a possibility it's just a connection issue, or a faulty ECM. Nice...

Just to document for anyone else running into this...

Had the CEL come back with a vengenance today. The VSC lights are back. Codes? P1300 and P1325 again. Cleared, then the VSC and CEL came right back. That time? P1300 only.

Anyway, checked voltage per Step 3 on Page 5 of this link above. I have 4.99 V for IGF1 and IGF2 (no issues with this circuit, but wanted a baseline).

Range is 4.5 V to 5.5 V.

Repair manual says to replace the ignitor coil at that point... But, when I replace the Numer 1 coil as suggested, my issue doesn't go away.

 

[OregonLC]

FWIW, I had the same thing with an 02 Pathfinder. Water in the main harness at the firewall. Fortunately for me, it happened immediately after the rinse and I traced the problem in short order. Very similar symptoms (code, stutter, no power, etc). It was on a warm day and I was able to dry the connector in a short amount of time and the problem immediately went away.

Is there any chance that you have some hidden corrosion on an engine ground? Perhaps water got under it and it has only a marginal connection that doesn't surface until vibration or hotel loads cause the voltage to drop. Doesn't explain the code for just No 1 cyl however.

 

[bamachem]

the crazy thing is that I'm just getting a bad signal for Number 1 and Number 6. Something funky other than Ignition Coils, and probably water is what my best guess still is at this point.

I checked continuity of the IGF1 harness from IC1, IC4, IC6, and IC7 between each coil pack and from the coil packs to the ECU. All is good at this point, so there has to be an intermittent loss of continuity, but doesn't seem to be with truck off.

I moved coil pack 6 to position 4 and coil pack 1 to position 2. This will tell me if it is the coil packs, the local wiring, the harness, etc. If I'm still getting the same P1300 and P1325, then I know it's in the feeds to/from the ECM or it's the grounding point at the pack - which I *just* thought of but haven't cleaned yet. If the code moves with the pack, then I know it's an intermittent issue with those specific packs and I can focus in on them.

There is a wiring harness "bundle" right over coil packs 5/7, then another splice/junction box behind the intake manifold next to the firewall <-this is where 6/7 ties into 1/4 before heading into the cabin to the ECM.

I got the bundle over 5/7 open, but everything was nice and dry. Can't get to the bundle behind the intake. Just no way to get back there to it w/o removing a LOT of stuff. I drove it a while and got things under the hood good and hot, and now it's sitting w/ battery terminal disconnected and hood open to make sure to get plenty of ventilation.

More to come...

 

[OregonLC]

Any updates? Problem solved hopefully!

 

[bamachem]

I'm stumped.

Engine Cold = Runs Perfect.

Get to operating temp (40% on gauge) and CEL triggers but no codes stored until later when the ATRAC lights come on. That hasn't happened since Sat, and until it does, I have no means of diagnosis. Once warmed up, the CEL will automatically trigger as soon as the engine turns over if you try to re-start. Once it cools down, it won't trigger until back at operating temp.

I have pulled every coil pack, checked for clean surface at ground, then added dielectric gel to the bolt before replacement. I've pulled every coil pack connecter and injector connector and sprayed with contact cleaner, then followed up with gel on them (and cleaned excess) as well.

Any ideas? The warm-up issue is bugging me. Any moisture should be gone by now, and should have the opposite effect anyway.

I moved the packs at 1 and 6 to 2 and 4 to see if/when the codes pop back up if they move. However, with no ATRAC lights, there are no codes on this.

Checked ground at battery, and added gel. Same for the connection from battery ground to fender. Checked voltage at ECU and it's good.

It is NOT a misfire issue as it has never listed a cylinder misfire code. It is an issue with the confirmation signal that the coil pack sends back to the ECU after a cylinder has an ignition. Surely this couldn't be a spark plug issue.... If so, then it would trigger a misfire (no spark).

It runs like a champ when "cold" before the light comes on. Once that happens, then the limp home takes over and it runs like schidt.

 

[NMuzj100]

Could be a connector expanding to create a short or to create a disconnect.

You could try to let the engine cool then warm one suspect area with a hair dryer and start to see if you get an immediate code. That would narrow your search area.

You could also warm the truck substantially and run until you get the code, get in a warm garage and then rerun your electrical tests including the spark test. Maybe with it warm you could locate the problem circuit.

Maybe shift spark plugs and see if the problem moves to eliminate that possibility. Does the coil ground through the plug ?

At this point you really are probably more of an expert than any shop you would take the truck to. Maybe consult with an auto electrician, explain what you have done so far and ask what they would do next.

 

[bamachem]

Good idea on using a hair dryer or heat gun to re-create a fault.

I did the electrical tests on the ECU with the truck warm and the Check Engine and ATRAC lights on to make sure. No issues with the voltage there, with the lights on.

The coil pack grounds via the single 10mm bolt that it uses to mount to the engine block. That's where I inspected for corrosion issues and added some dielectric gel to ensure a good, consistent ground.

I might try the spark plugs, but I really don't think there's any way that could cause this.

I think my option of last resort is to take the hood off for access, put some cardboard over the engine and crawl up on top of it to access the rear harness junction box behind the air intake manifold. That's the common area for the signal wire from coil pack 1 and 6 where they meet. That's also the area (near) where the ATF spilled and where I sprayed with water. I summize that it's possible that I either had some ATF get in there or the water PUSHED some ATF in there, which is now causing a short/disconnect. That would also be and explanation as to why it has not dried out because there's no way any water is left after driving ~100+ miles now at warm temps (ambient has been 60+ lately and it's hot under the hood at the back of the engine).

Good news is that I'm not driving it this week as I get the steering wheel recovered. Bad news is that I won't be driving it all week to get a good code and find out if the problem moved with the coil packs...

 

[bamachem]

Thought more on this and talked with one of our Service Techs (Refrigeration, not Autos) who is a gearhead and he made PERFECT sense.

When a modern CPU-controlled car is warming up to operating temperature, it operates in "open loop" and does not look at sensor feedback. Once at the correct temp (warmed up), then it begins to look at the sensor data to tune the engine for optimum performance based on the fuel maps, etc.

Since this only happened at "warm up", then the issue was probably happening when cold, but the computer just wasn't looking for the signal at that point, so the problem was being overlooked until the CPU changed to "closed loop" operation. At that point, the signal was absent, triggering the CEL.

I have been driving one of our company trucks all week and the Hundy's been parked here at work while the steering wheel was sent off to be recovered... long story.

Anyway, it's been sitting for 5-days now. I just went out and cranked it up and held 2200 RPM to get to operating temps, then let it idle at temp for a good 5-minutes with zero issues. Looks like the idea about moisture was correct and it has now evaporated, leaving me with the old truck I used to know!

I sure am glad the parts guy at my local dealer (Eastern Shore Toyota) let me return that coil pack that wasn't needed.

Nice to know that I don't have a coil pack, wiring, or ECU issue. Now, if I only had a steering wheel so I could actually drive it....

 

[AimCOtaco]

Looks like the idea about moisture was correct and it has now evaporated, leaving me with the old truck I used to know!

I sure am glad the parts guy at my local dealer (Eastern Shore Toyota) let me return that coil pack that wasn't needed.

Nice to know that I don't have a coil pack, wiring, or ECU issue. Now, if I only had a steering wheel so I could actually drive it....

Thats great news! Also good to remember to keep the closed loop v open loop in mind when trouble shooting, thanks.
I'm shocked they let you return a coil pack, that is excellent service. I keep hitting the NO RETURN ON ELECTRICAL PARTS thing with Toyota myself.

Glad you're running!