MickP2

A while ago i was getting intermittent CEL coming on. I got the following codes: KOEO 558, 332. I'm afraid i took the lazy option and swapped out the EGR solenoid for new one from O'Reillys. The 558 disappeared but i was now getting 332 and 334 CM. A few weeks later and 558 has come back, still accompanied by 332 and 334. i decided to do a bit of diagnostics:

Took off the EGR valve, cleaned it and can see the pintle moving when applying vacuum. It holds vacuum for 20 secs. Seems ok
Back on the engine, applying vacuum to the EGR valve causes engine to idle roughly, again indicates that EGR valve is working
Took some voltage readings on the DPFE sensor and see it increasing as i apply vacuum and giving the correct reading with no vacuum. Again, seems ok
With engine running, i check i am getting vacuum at EGR solenoid input. If i connect this directly to the EGR valve (ie cutting out the solenoid), engine starts to idle roughly. This seems to indicate vacuum source and lines are good.
I checked the resistance across the solenoid: 33 ohms (within the 30-75 ohm range). I am also getting 12v to the solenoid and have continuity from solenoid back to pin 33 in PCM connector. I also checked the resistances between pin 33 and various others (can't remember which but 37 and 60 were in there). All reading 250 Mohms so all good.

I'm not totally convinced by the solenoid. I tried to do the test where you check if it passes through the vacuum to the output side when revving the engine after it has warmed up and didn't see a reading. This is meant to be done when moving, and i was stationary so that might be a reason. Anyone have any bright ideas, or is this pointing to the PCM? Any definitive tests i can do before i go to the hassle of replacing this?

MickP2

Couple of further thoughts:
seems to me that the problem is either the solenoid or the PCM. Either the signal to operate the solenoid is not coming from the PCM or it is and the solenoid is not responding. I know that one of the connections to the solenoid is kept at 12v. What happens to the other connection in order for the solenoid to operate?

MickP2

I ordered a 12v supply (plugs into truck cigarette lighter). Tested the solenoid and nothing happening, no clicks, no nothing when apply the 12v. Returned it to O'Reillys and got a new one. Same thing happens. This time, they check a bit more closely and apparently the correct solenoid depends on one of the digits in the VIN (10th?). They have ordered the correct solenoid, should be in tomorrow

MickP2

So the 'correct' solenoid fails the bench test as well. What am i doing wrong? I apply 12v across the solenoid terminal and hear absolutely nothing. Does it depend on vacuum being present at the input? I don't see anything moving. On to my 4th solenoid now. Anyone got any ideas?

Steve83

The EEC grounds the other side of each valve to trigger it, just like it does with the injectors, coil, & IAC.

You can't necessarily hear the valve opening. It doesn't require vacuum to open, but that's the best way to KNOW if it's opening. If you can suck/blow through the valve's vacuum port, the valve is open.


(phone app link)


(phone app link)

All '87-96 EVRs, TABs, & TADs are identical, regardless of year or engine (though '96 trucks don't use TABs/TADs). Read this caption:


(phone app link)

MickP2

Thanks Steve. I have put a new solenoid in, and the CEL went off for 25 miles or so (just long enough to get my hopes up). Now it is back on intermittently, i will read the codes as soon as i get a chance.
Testing the solenoid using the vacuum port makes sense rather than listening for a click

MickP2

Codes as before: O - 558 C - 332, 334

Did a couple more tests - attached vacuum from engine source to solenoid and attached vacuum gauge to the solenoid output. Applied 12v to the solenoid +ve and when i grounded the other side, i got a reading on the gauge. Then i attached both engine vacuum hoses to the solenoid, ran the engine and did the 12v test - engine almost dies. Repeated a few times, but this makes me think everything in the EGR system is working. I have tested i am getting 12v at the connector and there is continuity between connector and pin 33 on the PCM. The only conclusion i can come to is that the PCM is faulty. Anything wrong with that logic?

MickP2

Edit

Steve83

The first step in diagnosing any fault code is to confirm that the indicated condition actually exists. If you have a code for a circuit fault, and the circuit is NOT faulty in any way, then the EEC is the only possible cause for the code.

MickP2

So back in May i had concluded that the PCM/ECM module was bad on the basis that i had tested every other bit of the system and it worked. I didn't think it was worth the expense of changing the module...until one came up on Amazon for $60. Installed it and still got the same code (558). Rather dejected, i let it be until yesterday when i noticed that the connector to the solenoid had come apart. Pushed it back in, and NO CODES! Now, it might all go wrong tomorrow, but i am taking this as a victory, however short-lasted it might. Thanks all for your help with this