can only a Ford dealer flash a PCM?

[mikeh1]

Can only a Ford dealer flash a PCM?

Getting the same error code, P0155, even after the indicated sensor has been changed (bank 2 sensor 1), checked wiring harnesses and even swapped with other HO2S sensors. error code is also intermittent, one day it's OK, next day, error code. Only thing left is PCM, which I understand can be "flashed" or reprogrammed to original specs. New one is about $470.

 

[mikeh1]

PCM was flashed, still has problems, dealer said $400 more to fix

nice of Ford to keep it's dealer mechanics in business with these sort of games, with the computer giving false error codes, so the mechanics can empty your wallet.

 

[2000StreetRod]

P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

As I recall from one of your earlier posts you have an OHV and this code comes and goes. Your mechanic has checked the wiring and swapped O2 sensors around but the code doesn't change.

I don't have a 1997 wiring diagram but I suspect your O2 sensors are wired like my 2000 in that there is a common heater source for all O2 sensors and an individual connection to the PCM for the path to ground. I am surprised that your mechanic said you have four O2 sensors. The later models only have three O2 sensors for the OHV engine but there are four O2 sensors for the SOHC.

Anyway, the PCM has no independent way to verify the O2 heater circuit. It simply measures the current flow for each heater and reports any abnormality. Bank 2 sensor 1 is the precat O2 sensor on the driver side. It is the easiest of all the sensors to get to. Unfortunately, DTC P0155 does not indicate if the heater circuit malfunction is excess (short) or insufficient (open) current.

My suggestion is to trace the wiring from the O2 sensor back (yellow/light blue wire) toward the PCM (destination) and from (light blue/orange wire) the fuse 13 (source) in the battery junction box. This is what a Ford technician would have to do to find the cause of the problem. I'd pay particular attention to the O2 electrical connector and the wiring near the exhaust pipe. Also, make sure the wiring is not getting caught on the transmission shift linkage.

 

[mikeh1]

my mistake, only 3 O2 sensors. PCM was flashed, but it turns out the wiring loom was chafing, so my mechanic owes me some time under that hood again. The dealer wants $400 to fix, my mechanic will probably charge only $250. What a PITA all this computer and sensor nonsense causes, but I probably wouldn't be getting 20 mpg either.

I miss my '65 Le Mans, if something was wrong, you knew EXACTLY what it was (most of the time)

also, thanx 2000StreetRod for the info