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

[nomembername]

You're definitely going about the diagnosis in the right way.

If the issue returns, also look for burnt plug wire boots, or anywhere plug wires might be contacting sharp parts (like gasket edges) or hot parts (like exhaust manifolds).

Pull each plug wire (one by one, so you don't lose track of which goes where) and make sure the ends are still securely in the wire cores. At this time, also check to make sure no plugs are cracked or fractured.

There are a lot of funky electrical issues that happen when metals expand that don't exist when metals are nice and cool and contracted. Being wires, the problems could also come and go as the truck bounces over bumps.

 

[bamachem]

Thanks. (Pssst: Hundys don't have high-voltage plug wires. They have "coil packs" at each plug containing a capacitor that provides high voltage current when triggered by the ECU.)

 

[nomembername]

Thanks. (Pssst: Hundys don't have high-voltage plug wires. They have "coil packs" at each plug containing a capacitor that provides high voltage current when triggered by the ECU.)

Same principle applies. A cracked plug can arc, a loose connector can arc, a burnt boot can arc... whether it goes to a wire or a tower-style capacitor.

 

[bamachem]

Oh, I know, just bustin' your chops a bit.

For the record the coil packs have 4 wires on the clip. This is how I understand it:

12V+ Lead for Power
Ground/Common
Ignition Signal (5V) that triggers the Ignitor to fire the plug - only energized at time of firing - from ECU
Ignition Confirmation - this is a continuous 5V signal that is interrupted when the coil pack fires - only dead at time of firing - from ECU

Not necessarily in that order

 

[bamachem]

I got the steering wheel back today, hooked everything up, and it drove great for about 5-min. Once it got up to operating temp, the CEL came back. No VSC/TRAC lights until about a half-hour later after I stopped for gas and had to re-start. Pulled the code.... P1300

This is so freaking frustrating!

Next on my list:

Run a "jumper" from the Ignition Circuit Signal Wire on Coil Pack 1 directly to the plug on the ECU. That will tell me if it's in the wiring or not...

 

[bamachem]

I'm tossing in the towel. Just dropped it off at Springhill Toyota for a diagnostic. It will probably run around $100, but they guarantee they will find the problem or they won't charge me. When they do have an answer, I'm going to stop by and chat with the tech to see what he did to determine his conclusion - and it better not be "I pulled the code and it's a bad coil pack"... I warned them up-front that it has me stumped and that I've already been through the FSM, Repair Manual for P1300, and tried a coil pack and also moving the coil packs around. I'll post up results here... hopefully this afternoon.

 

[Trunk Monkey]

Yeah, this will be an interesting one to put to bed. Hopefully it's something simple.

 

[bamachem]

If it is, then I'm going to feel like a moron... but a HAPPY moron without a CEL nagging me!

 

[bamachem]

Bad ECU. $1300+ estimate for replacement.

Since I recently lost the master key, I'm going to see if Toyota corp would comp a ECU with the purchase of (2) keys under these circumstances.

 

[bamachem]

Called dealer and they "didn't know" about the comped ECU's for these LC's, and considering how few of them there are around here, I believe them.

Anyway, they referred me to Toyota Corp. I called, told them about how I've lost my master key and now it looks like I need an ECU in order to get new keys added. Let them know I wasn't happy about being quoted $1600+ for two keys and that I expected help on this.

Took my info, checked on availability of the parts and eligibility via the VIN. Got confirmation back that they will indeed comp the ECU swap if I agree to pay for (2) new keys plus the labor.

I'll re-program my current (2) keys as well, and have them as spares in a safe place. Not a bad deal in the end.

Sure wish this would have been a bad coil pack, but I really can't complain about getting some extra keys (new master) and no CEL for that price...

 

[NMuzj100]

I would want an assurance that if the problem still exists with the new ECU that you could return it.

A used ECU would be a lot cheaper.

EDIT: Well that seems reasonable. I hope it solves the problem.

 

[bamachem]

$547 + $47 diagnostic. I have a dealership coupon for $75 off a $500+ purchase on parts or service, knocking it down to $519 total.

For that, I get (1) new Master w/ Remote Fob, (1) new Transponder Key (no Fob) as a spare, both of my existing keys re-programmed, and a new ECU.

Meh, can't complain too much. Cheaper than selling this one and getting an 06+.

 

[bamachem]

Chatted w/ the tech when I went to pick it up.

He did the following to diagnose:

• Hooked up Laptop and pulled codes: P1300 (ongoing) and P1325 (intermittent)
• Cleared codes
• Moved #1 and #6 coil packs to #2 and #4 positions
• Re-crank and pulled codes - P1300 only
• Cleared codes
• Checked Voltage at ECU per FSM - Good
• Checked Voltage at #1 Coil Pack - Good
• Checked continuity of Wire between ECU and Coil Pack - Good

However, whenever he cleared the codes, the Check Engine Light wouldn't go away, but the VSC/TRAC lights would go out.

Based on this, and the fact that the diagnostic steps point to ECU, they are recommending the ECU change.

When I picked it up, I got about 100-yards out of the dealership parking lot and the driver door unlocked itself. 15-20 seconds later, it did it again. It is now doing it at random intervals even with the truck shut off. Nice. Now I can lock the truck, even with the key FOB, and the truck will unlock itself but it doesn't set off the alarm.

 

[bamachem]

The CEL will not clear by either pulling the ECU fuse or disconnecting the neg terminal of the battery.

Also, cranked this morning, got the CEL/TRAC/VSC lights, and it drove normal. No limp-home, reduced timing/power crap. About 6-7 miles into my commute, the dash lights went off by themselves. Yes, the code cleared itself while driving down the road. About 3-miles later, the CEL came back on... LOL

I'm just crossing my fingers that the ECU doesn't give up the ghost before next week when the new one arrives...

 

[jttexam]

Glad you got that resolved, what a beating.

 

[OregonLC]

So do you suppose that a water-induced short was the incipient factor in the ECU fail? Or is this just a coincidence?

While I was hoping (for the sake of your troubleshooting) that it was a water related problem, in the back of my mind this bothered me because it plays against all of the stream forging pics posted all over this forum. I suppose there's a difference between submerged and sprayed, but still...

 

[bamachem]

Good point.

To be honest, I'm not sure on what may have triggered this, but I strongly suspect that it was the rinse that may have grounded a wire, shorting something out on the board in the ECU. It's the most plausable scenario considering the timing of the initial CEL coinciding with the "wash down" under the hood. However, at the same time, there is no open wiring anywhere along that circuit, so there should theoretically be no place for the wire to short, except for right at the plug where it connects to the coil pack.

Maybe it was coincidence. Maybe it wasn't. I'll never know to be honest...

However, I do know one thing. I will be EXTREMELY careful from here on out when rinsing things off under there. The nozzle on the hose will be GENTLE, and NO POWER WASHERS ALLOWED!

As far as water crossings go, submerged water doesn't have the force to get into the cracks and crevicies that a hard spray may be able to penetrate into. I would have no worries doing some moderate water crossings. Besides, the wiring loom is at the air intake, above the coil packs. If you get water THAT high, then you've got a LOT more worries than a short if you don't have a snorkel and a waterproofed truck.

 

[mtnracer]

Did the new ECU resolve the issue?

 

[OregonLC]

If not, the 'new' 2006 LC will!

 

[bamachem]

Yes, the truck runs perfect - as expected - with the new ECU and there are no codes... Problem solved!

Now my new problem is that I have a week to find an 06 before I have to deliver this 2000 to it's new owners.