Limp mode

my 95 tacoma kicks in and out of limp mode randomly. When this occurs the check engine light kicks on and off. My self and the dealer have put a scanner on it when this happens and it won't connect. So I tried a used computer and it's the same thing.

 

Does it ever set a code? If so what code?

 

I thought Limp mode was only on the 03-04 and previous years were cable driven?

OP more details about your truck would be helpful too (engine type, cruise, trans, etc)

 

It is a 2.7 L 5 speed. It will give me exhaust codes but that's because I cut the cat out thinking it was clogged up. Whenever it starts to act up scanners won't connect to it.

 

Do you mean the MIL light flashes on and off??

Something is wrong is your OBII plug corroded ??

Rodents chewing on wires ??

Without the Cat the light should always be on unless you keep clearing the code .

You changed ECM`s your sure it was good??

Ecm get wet ??

Bad connection some place .

As far as I know 95.5 did not have a limp mode

 

There are fail-safe modes, like if the coolant temp sensor isn't working the computer assumes the coolant is at 180°F. Same for other sensors like the MAP.

But how do you know it's in limp mode if the scanner won't connect? I mean what's the difference between limp mode and just running really bad?

Perhaps an electrical problem like low voltage? This would cause the engine to run bad and the computer to not communicate.

 

The factory repair manual has a fail-safe chart for 1996. It's limited to P0100 (MAF), P0110(IAT), P0115(ECT), P0120(TPS), P0135(O2), P0141(O2), P0325(Knock Sensor), P0336(CPS) and P1300(Igniter Circuit Malfunction).

 

When the CEL/MIL flashes like that it is the PCM telling the driver STOP you are damaging the motor or the catalytic convertor. Since you have the cat cut out the the PCM is going into limp home mode. You might have to investigate the O2 sensor bypass hack that I have read about.

 

I was under the impression that limp mode just added a bunch of fuel and pulled a bunch of timing. And limited throttle on vehicles that are TBW.

 

Isn't 'limp mode' also referred to as 'open loop' ?

 

No. There are special fuel maps and timing maps used if the ECU determines the conditions are "abnormal".

On my Speed6, there are "abnormal" fuel, timing, throttle control, and load maps. In addition to the standard OL/CL maps.

All the tuning I do on that car, I'd like to be able to tune this Taco. Strongly considering the Bluetooth OBDii adapter thingy so I can at least monitor some things. I already have TorquePro.

 

open and closed loop refer to if the PCM's base injection/timing maps are modified by the O2 sensors or not.

 

I log a lot of data on my turbo truck. When I threw po325 for knock sensor the truck goes to "limp mode", the stock ECU pulls timing and adds fuel. That is open loop, the ECU is ignoring all the sensors and feeding it a pre calculated tune.