2007 1.4 D4D P0487 problem with twist(s)

March 10, 2020

Hi All,

I'm flummoxed by my little Yaris, even after reading others with P0487 problems.

I had the P0487. I unplugged the EGR loom, checked it, cleaned the contacts, looked over the solenoid, reconnected it and cleared the code. A few days later, it came back so I put in a brand new EGR with solenoid and cleared the code.

A few days later it came back shortly after starting the car. After driving for ~30min I could clear it and it would stay clear until the next morning. Repeat pattern for several days.

Car become a tiny tiny bit harder to crank when cold but not a problem. Now P0487 re-appears the instant the car is started and will return immediately upon clearing. The car idles fine, 800-900rpm, the low end response is good but there's no top end above ~3000rpm and my fuel economy has tanked. So, I did some OBD monitoring:

1. MAF shows ~9-45 g/s ( idle -> WOT ) which seems fairly normal.

2. Throttle Position Sensor stays in the range 45%-48% ( idle -> WOT ) which seems very wrong but then why does the car drive fine under all conditions except heavy load?

3. MAP Sensor reads ambient ( 101kpa ) with the engine off but... 99kpa-100kpa at idle; no drop to what, I think, should be around 55kpa-65kpa(?) with the throttle closed and the engine sucking more vacuum. Max load gives around 174kpa. Vacuum leak between the throttle body and manifold? Except that ( just from my googling - ahem ) I don't think my driving symptoms fit.

4. Load_PCT 0.0. I used to get a reading on this, can't recall what. Then it was sporadic and now I never get a reading, it's stuck at 0.0 - no idea why

5. Battery is at 12.7V and 14.3V with the alternator running.

Obviously it's not the EGR itself since that's been replaced. If it's a vacuum leak why does the car start, idle and drive ok except for the top end. If it's the throttle position sensor, why does the throttle respond nicely up until top end load? So the car and scanner think I have EGR, TPS, MAP and Load_PCT problems all at the same time??

I don't believe it for a second.

I'm going to check the ground wire and the Battery terminal contacts but they 'look' ok. I'll also put my multimeter across the EGR pins on the loom, I assume it's just straight through on all six pins to the alternator side but I don't know.

Does an obvious answer jump off of the page at anyone because I'm almost reduced to just randomly replacing stuff, e.g. the above sensors, maybe the whole PCM, the whole throttle body, the wiring looms ( which ones? ) etc. until maybe one day and many more £100s later, the error goes away.