I have a 02 l300 with 60k miles two weeks ago I was on the interstate and it out of no where started running rough then shut off and wouldn't start back up. I got it towed to my house and found that the fuel pump was not working so I replaced the pump hoping everything would be ok. After the new pump was installed I started it and it was just running really rough, misfiring and stalling on idle. Since then I have replaced my MAF sensor, coil packs and plugs. I checked my injectors and found one was damaged on the spraying end of it so I replaced that one and cleaned the rest of them. Nothing has made a difference at this point and I don't know what to do/how to determine what is thr cause of the misfiring, the p1780 and p0502 code being thrown. Has anyone experienced something like this that you might have some guidance on how to resolve these issues?

 

I will start with have you replaced the timing belt? I will look at the codes when I get home tonight. the mileage interval is 100,000 but time is also a factor. I bought my LW300 last year and at 96,000 miles and 20 years I was lucky.

 

Both P1780 and P0502 are transmission control module codes based on faulty engine control module information.

P1780 is Torque Reduction Signal. The transmission control module received an invalid torque reduction signal from the ECM. The TCM went into self protection mode, went to max line pressure.

P0502 is an unexpected vehicle speed output sensor signal. Speedo will drop out for the key cycle and the transmission will go into self protect mode.


I would look at your engine running problems first.

 

The timing belt is probably coming apart. That is what I would look at first. The car has four camshafts and if the belt is failing you will have catastrophic engine failure.

 

 

Would suggest timing issues related to timing belt as LW mentioned, could had led to detonation......that will torch anything.

 

Compression check will confirm the ugly