This is a complicated question revolving around coolant temp and EGR enable.

I have been looking at $42 code for setting EGR enable from coolant temp, and have a bunch of questions. i will start with where it begins and follow it to where I am now.

In the REAL TIME SERVICE ROUTINE 3

EB5A: LDX #$D1B3 ; EGR PARAM'S
;
EB5D: LDAB L0006 ; STATUS
;
EB5F: LDAA 0,X ; 48c COOL FOR EGR ENABLE (1K PU) TBL 3
EB61: CMPA L00E3 ; COOL, 1k pu
EB63: BLS LEBA5 ; BR IF COOL VAL LT THRESH

I understand the code here, this is just for reference to what I am trying to get at.
At EB5F it loads the accum. with the EGR enable count and then compares it to L00E3. This is where I seem to start to loose it.

The coolant temp in the ALDL stream is located at the 4th position and the code looks like this.

LD4ED FDB $0025 ; 4. COOLANT
; see table 1

LFAFF DECB ; DECR DIAG MSG LINE COUNTER
FB00: ASLB
FB01: ABX ; ADJ ADDRESS INDEX
FB02: LDX 0,X ; GET ADDRESS FROM TABLE
FB04: LDAA 0,X ; GET VALUED FROM ADDRESS
FB06: LFB06 STAA L007C ; CURRENT DIAG OUTPUT VALUE

here, when X=4 (the fourth value in the ALDL stream) it loads X = $0025 at FB02 and then gets the value stored at $0025 which it outputs to the data stream.

Here are my questions.

1) where does $00E3 come from
2) is $0025 already converted to degrees when it is stored
3) how do $00E3 and $0025 relate to each other.

 

Okay, I figured out that $0025 is raw A/D counts, so that is answered. Now if I can just relate $0025 to $00E3 I will have the answer I need.

 

I figured out the $e3 and $25 are same thing by following coolant temp routine through the A/D conversion until it is stored. I can now go figure out EGR enable problem

 

Location $25 is the raw CTS ADC value. This is used in the ALDL stream for diagnostic purposes. We want to see exactly what the ECM is seeing.

Location $E3 will be the same value unless the ECM thinks that the CTS is in error. In this case the value in $E3 will be the default value as defined in the calibration.

Being that these are the ADC counts will need to use the table to know what value equates to what temperature. IIRC, that table is included in the '7747 hac.

RBob.

 

Thanks RBob, I finally figured it out last night. The trick was following the A/D code for coolant temp. Now I need to figure out why changing the EGR coolant Temp enable to something higher than the coolant temp will cause the vehicle to die.

 

So far the one's marked 1k pup need that conversion table, one's not marked 1k pup are just X and accurate. Does that sound right?

Looking through several old $42 masks I found at least 7 different conversions.

 

i'm sure that this question has been asked many times before.. lol but here it is one more time.. the engine fans are controled by the ecm and a chip... if so is there a chip i can get so my cooling fans turn on before temp gets to 220 and above when i have to sit at stp lights in town.... or what else can i do???