Crank no start (1 Viewer)

[jjjewett]

I am having a crank-no start issue on my 1999 LX470.

It is intermittent but increasingly frequent. Will just crank until the battery gets low. It has never stalled, stuttered or died on me once it starts.

175k miles, new starter, new spark plugs, new ignition coils, good battery.

The key light goes off when I insert the key into the ignition cylinder.

I pulled the codes and it had a B2796 - No Communication In Immobilizer System

I have experienced this with 2 different keys both OEM fobs one with a new battery, will change battery on the other.

I have pulled the outlet off of the fuel filter and verified fuel is pumping out of the fuel filter at crank.

I have connected the battery directly to the EFI relay per this advice: EFI Relay Bypass Kit (Immobilizer Fix) for UZJ100/LX470 - https://forum.ih8mud.com/threads/efi-relay-bypass-kit-immobilizer-fix-for-uzj100-lx470.952811/page-24#post-15654555

Reading through the various threads it seems like the CPS might be something I take a look at but I am stumped.
Is there a way to verify "no spark" like pulling a coil?

-JJ

 

[NickSonoma]

I am not a mechanic.

What happens if you remove the air filter and try to start it? Have you checked the entire air intake for obstructions? Have you replaced your fuel injector grommets?

When my starter failed, it was catastrophic and not a result of it slowly losing its chooch. The replacement starter wasn’t noticeably stronger. Taking care of the maintenance associated with removing the intake manifold seemed to make sustained combustion catch a lot sooner. I cleaned the intake with a refrigerator coil cleaning wand and a gallon or two of degreaser.

 

[medtro]

FSM has a diagnostic section on how to check for spark.

 

[jjjewett]

As an update I cleaned the MAF, throttle body, and cracked the gas tank cap (also ordered a new one) and it is starting 9/10 times now! 1/10 it will start then die immediately. Anything else I should be looking at? throttle position sensors? Charcoal canister?

 

[REDrum]

Could be a bad usable link off the hot side of the battery. When it's turning over, what doe s the dash look like?

 

[Import Driver]

Tap on the main relay.

 

[jjjewett]

Tap on the main relay.

Thank do you mean the EFI relay?

 

[2001LC]

So was B2796 cleared and it came back? @medtro, will this DTC come back with bypass?
Did you do the EFI bypass, in response to fail immobilizer crank no start?

BTW: Key FOB battery, has no effect on immobilizer.

Sound, a lot like fuel delivery issue. But seeing, a good fuel follow out filter, just after a crank no starts event. Suggest, a good fuel pump.
But that test is a bit tricky. Since, intermittent fuel pump on start-up attempt, is sign of a bad one.
See fuel flow, attach line and no start after. Or no fuel flow. Are a bit more conclusive.

I'd check for spark and I'd look very close at wires and wire housing blocks, for cam sensor and CPS. So often, CSP oil pressure wires routed wrong, and rub on serp belt. Or a wire housing block, not locked in.

If everything is checking out okay. I'd be inclined to R&R fuel pump & filter anyway. I've found fuel tanks, loaded with iron (remains of rust). Which is hard on pumps and filters.

 

[medtro]

So was B2796 cleared and it came back? @medtro, will this DTC come back with bypass?

The bypass is not to fix B2796, which is the output when a key that does not have a transponder chip is inserted into the key slot or if communication between the key and transponder key ECU is not possible.

 

[2001LC]

The bypass is not to fix B2796, which is the output when a key that does not have a transponder chip is inserted into the key slot or if communication between the key and transponder key ECU is not possible.

With EFI bypass installed. Is registered chip key and or communication, still required to start?

 

[medtro]

With EFI bypass installed. Is registered chip key and or communication, still required to start?

Correct.

 

[Import Driver]

Thank do you mean the EFI relay?

Yes.

 

[REDrum]

Yes.

Just replace it. And the other EFI relay too. Check all fuses on the fusible link block too, Main 100 amp fuse is vital. I would double/triple check fuel pump is running on crank, not just fuel flow when you crack the fuel open.

 

[ike84]

It may help to back up for a second and think about the systems involved in this process. Our keys use rfid-transponder coils, built in to the fob head. Around the lock cylinder there is a small antenna coil. When you put the key into the cylinder, the coil energizes the transponder coil and causes it to transmit it's signal, which is sensed by the coil. That signal is then transmitted to the immobilizer. The immobilizer then compares the signal against what is stored in memory. If the signal matches, the immobilizer tells the ECU to "fire away". Without that match, one or more systems (spark and fuel delivery are the usual two) will not operate. Thus, you will get a "crank but no start".

The are certainly other things that can cause crank without start. @2001LC has brought up one of the most common - rust in a fuel tank. And he is definitely right, it can be a PITA to figure out that is the culprit in some circumstances.

However, if you are pulling a code that says your immobilizer is not talking to the ECU, I would start by thoroughly inspecting all the wiring involved and look for signs of damage or corrosion. These systems are very effective, but can be sensitive.

The easiest way to tell if this is your issue would likely be whether your security light goes off when you insert the key. If it turns off every time except for when the truck doesn't fire, you know what you're dealing with. On the other hand, if the security light goes off and you still can't start, then move on to mechanical (fuel system) or other electrical issues (corroded relays).

And no, there is no bypass for this system. You can fool them, but not bypass them. That efi relay "fix" only addresses a shotty design in the fuse box. You still need the system to function as described above, regardless of where your efi relays are drawing power.

 

[medtro]

And no, there is no bypass for this system. You can fool them, but not bypass them. That efi relay "fix" only addresses a shotty design in the fuse box. You still need the system to function as described above, regardless of where your efi relays are drawing power.

To the best of my knowledge, this Cygnus has the immobilizer system bypassed.

Africa Build 2.0

Prologue Years ago I moved to Zimbabwe and built a truck named “Matterhorn” – see the build thread here. I went away for a few years, and now I’m back, a little further North, in Zambia. I learned some lessons after having to part ways with our beloved Matterhorn at the end of my Zimbabwe...

forum.ih8mud.com

 

[2001LC]

I am having a crank-no start issue on my 1999 LX470.


The key light goes off when I insert the key into the ignition cylinder.

I pulled the codes and it had a B2796 - No Communication In Immobilizer System

-JJ

"Security light off, key in". Yes!

B2796" Was this DTC cleared, and came back after a recent crank no start?

 

[Mauser]

To the best of my knowledge, this Cygnus has the immobilizer system bypassed.

Africa Build 2.0

Prologue Years ago I moved to Zimbabwe and built a truck named “Matterhorn” – see the build thread here. I went away for a few years, and now I’m back, a little further North, in Zambia. I learned some lessons after having to part ways with our beloved Matterhorn at the end of my Zimbabwe...

forum.ih8mud.com

Pretty sure @LexusV8 Engines can bypass the immobilizer. WIRING & ECU SERVICES FOR ENGINE SWAPS - https://forum.ih8mud.com/threads/wiring-ecu-services-for-engine-swaps.1353644/#post-15777371

 

[jjjewett]

Thank you for all of the responses.

In an effort to eliminate any key transponder issue I ordered a new key fob. The key transponder was programmed and the fob was programmed. I still got a crank/no start with the new key with the key light turning off on each attempt. I have not received the B2796 code since using the newly programmed key.

I am now 5/5 on starts subsequent to driving around the vehicle for 20 miles. The throttle body was really dirty and I am wondering if that was the culprit.

Things I have changed since getting the crank/no start are cleaning the MAF sensor and the throttle body.

 

[jjjewett]

It may help to back up for a second and think about the systems involved in this process. Our keys use rfid-transponder coils, built in to the fob head. Around the lock cylinder there is a small antenna coil. When you put the key into the cylinder, the coil energizes the transponder coil and causes it to transmit it's signal, which is sensed by the coil. That signal is then transmitted to the immobilizer. The immobilizer then compares the signal against what is stored in memory. If the signal matches, the immobilizer tells the ECU to "fire away". Without that match, one or more systems (spark and fuel delivery are the usual two) will not operate. Thus, you will get a "crank but no start".

The are certainly other things that can cause crank without start. @2001LC has brought up one of the most common - rust in a fuel tank. And he is definitely right, it can be a PITA to figure out that is the culprit in some circumstances.

However, if you are pulling a code that says your immobilizer is not talking to the ECU, I would start by thoroughly inspecting all the wiring involved and look for signs of damage or corrosion. These systems are very effective, but can be sensitive.

The easiest way to tell if this is your issue would likely be whether your security light goes off when you insert the key. If it turns off every time except for when the truck doesn't fire, you know what you're dealing with. On the other hand, if the security light goes off and you still can't start, then move on to mechanical (fuel system) or other electrical issues (corroded relays).

And no, there is no bypass for this system. You can fool them, but not bypass them. That efi relay "fix" only addresses a shotty design in the fuse box. You still need the system to function as described above, regardless of where your efi relays are drawing power.

Thank you. I have experienced the crank/no start with the security light off. I experienced the crank/no start with the security light off and the efi relay bypass wire. I pulled the fuel line off of the output side of the fuel filter and got a good stream of fuel coming out on crank. I am inclined to believe this was an air issue based on the experience of cleaning the throttle body and MAF sensor and experiencing 14/15 starts and now 5/5 after driving around for approx 20 miles.

 

[jjjewett]

"Security light off, key in". Yes!

B2796" Was this DTC cleared, and came back after a recent crank no start?

This DTC was cleared and did not come back despite a crank/no start. This was before I cleaned the throttle body and MAF sensor.