Preliminary scanning of one of the schematics I have (up to 99 and generalized) , which means not 3rd generation like your vehicle, may have some information that may be of assistance. The general functionality and type of sensors didn't really change over the years to my knowledge. So I believe even the older generations of s cars supplied a 5 volt reference signal to the same general group of sensors.

Disclaimer out of the way, here is what I see on first glance:

There is a shared 5V output circuit from PCM B5 and B6 (Both on the same circuit externally)
Feeds TPS, MAP, Handwheel Sensor, not quite sure about the air intake sensor labeled as MAT. It is shown coming off a different pin B7 and is not labeled as a 5 volt feed.

However, pins D1 through D4 share a common ground circuit externally for all four of the devices named above.

The code triggers if the five volt reference drops to 3.5 volts or below.

I also found the coolant temp sensor feed, which I am almost positive has a five volt reference sent to it, but that again is on a different circuit/pin coming out of the PCM.

​​​​​​My out of the blue guess is that open circuit at the connectors you will read 5 volts, but when connected, you will read below 3.5 volts. To troubleshoot, you would have to disconnect all devices using the 5 volt feed and test each one individually in order to determine the offending party.

It may also be one of those wonderful lost ground or intermittent ground situations not necessarily at the PCM but wherever those connections come together if they do. but those pins D1 to D4 should each individually be grounded.

 

I should also emphasize that the company may have tested the five volt output on the PCM. The question is what were they using as ground when testing it.

They may not have checked to see if those grounds on the D connector are actually internally grounded as they should be. You can check by measuring the resistance between any one of those pins and chassis ground since that is where the PCM gets its ground.

 

And.........

 

Sorry for the delay. I have so many projects and this one has taken a low priority since I have other transportation. It does start and drive but the two codes (P1635 and P0327) continue and will not clear.
Also it has been unusually cold here, so I haven't worked on low priority projects, like this one. But it is time.

I don't think I reported that the Inlet Air Temp Sensor has good +5 (+4.99volts).
Also received and installed new Knock Sensor but that code P0327 (Knock Sensor Circuit Low) still reported.

One additional symptom observed - I started the car with each of the +5 sensors disconnected (one at a time) and got appropriate code for each, EXCEPT for the EGR, no error message when disconnected. Not sure what that may mean.???

I need to follow up on the latest suggestions like "coolant temp sensor" and "disconnection all sensors" for +5 measurements.

Thx and again apologies for the delayed reply,
Larry

 

Do you have a scan tool? Codes point to what we want to look at in the data-stream and not so much as to replacing parts.

 

Yes (on code scanner), that's how I know the two codes P1635 and P0327 continue and can not be cleared.

I've tried watching the live data - but all appear to move, as I would expect, as the engine warms up.

Still no clue why no EGR code when the connector is off (engine running).

Also not sure what other sensors might need / affect +5V - looked at EGR, MAP, Throttle Position, inlet air temp.
all have 4.99V with connector on and off with key in run but engine not running - 5.02 with engine running and all connectors in place.
Haven't checked the coolant temp sensor, yet.

Also the Knock Sensor is still reporting as low (P0327) even with a new sensor and checked the wiring with good continuity.

Thx for any insight anyone can give.
Larry

 

EGR will not set UNTIL parameters call for it, and it does not open eg(open)
Suggest a "bonding" ground installed between engine/chassis
measure res between PCM and GND

 

Have you tested the body and frame grounds while loading the battery and alternator with heavy load. High Beams on and suchlike.

 

• P0403: EGR circuit malfunction.
• P0404: EGR circuit range/performance.

 

Bingo!