Question97 lhs no start
Question: Subject: 97 lhs: won't start, no check engine light
Question: QUESTION: Hi Roland, Just like to say, your wisdom has helped me through most every problem I have had with this car! Thanks! Anyway, went to leave for work today, and the car turns over but will not start. I replaced the ignition switch last winter, so I wouldnt think it is that. What bothers me is that, I have had the check engine light on for awhile, and the codes read for basically a bad ground, and would go off and back on while driving, I think it was code 12, today I get no codes at all when I do the off on off on off on, yet it just keeps turning over. The check engine light doesnt even go on when I turn the key forward???? I am stumped!
ANSWER: Hi Ken,
The code 12 and the lack of a check engine light leads me to suspect that one or the other of the battery supply circuits to the engine control module are not connected. The code 12-related
wire is red/white and it comes from the power box under the hood from fuse B (20 amp) which is the next to rearmost fuse of the inboard row of 5 fuses. So verify that both sides of that fuse show 12V and/or look at the fuse closely for a subtle crack if not a frank blowout. It is connected to pin 3 of the pcm. The ignition switch provides the other power circuit thru fuse 18 (10 amp) in the fuse box behind the dash (remove access to check that fuse, similarly). It connects to pin 9 of the pcm via a dark blue/white wire. Once you get the check engine light back 'on' the engine may start or at least you can get any fault codes.
Thanks for the kind words on previous problmes. You are welcome.
Roland
---------- FOLLOW-UP ----------
QUESTION: Ok, checked both fuses, both are fine. Upon checking voltage, one side(left if facing front of car) shows 10 to 12 volts the other shows 0.
ANSWER: If you are speaking of fuse B then that indicates the fuse isn't conducting, probably has a crack in the wire you can't see.
---------- FOLLOW-UP ----------
QUESTION: Hello, ignore my last post!! Voltage is good through fuse, just to be safe, I ran up the street and grabbed a new one, so thats not it.
Answer: How about the other fuse and also check for voltage at pins 3 (all the time), and 9 when the key is in 'run' and in 'start' at the pcm plug? Just pull the plug and measure or stick a pin through the wires' insulation to test for voltage. Also, because you mentioned grounding, test that pin 5 is showing a short to chassis ground.
If those voltage check out, then listen for the fuel pump to run for about a second when you turn the key to 'run'; and check for spark while cranking the starter motor by means of a screwdriver inserted into a spark cap and while holding the insulated handle place the shaft of the driver 1/4" from the cylinder head while a helper cranks over the engine.
Hi Roland, It wouldnt let me ask any more follow ups, so I put prior conversation in here. Other fuse is fine, when I pull out pcm plug, do you mean pin 3 and 9 on the top row, from left to right? They really couldnt have put it in a worse spot!
Answer: Viewed from the terminal side of the plug, with short tab up, 1-20 are the top row. L to R. There ought to be some numbers engraved one side or the other of that plug, or verify wire colors if visible. How about the sound of the fuel pump, any spark when cranking?
Roland
Hi again!! ok no power at pin 3, power good at pin 9. no spark, and doesnt sound like fuel pump is charging up. This all really sucks, too because it is single digit temps with the wind chill, so I can only do a little at a time!!
Answer: Hi Ken,
Let me clarify the pcm plug situation. I am using the '94 manual which has a single 60-pin plug at the pcm, correct? If not let me know and we'll revise which pins are in question. So if pin 3 shows a red/white wire then that is from the battery via fuse B as I told you earlier. It also is spliced to pin 56 of the tcm plug and to the front pin of the tcm shutdown relay in the powerbox, front row. If you have power on both sides of the fuse B then you should have power everwhere else I described, or there is an open wire between the fuse and pcm pin 3.
Roland
Think it must be different, I have a blue and white wire going to pin 3
Answer: Please check that again. If you have the 60-pin plug I show a red/white on pin 3 and a dark blue/white on pin 9.
If by chance you have 2 40-pin plugs (as shown in the '98 manual) then the red/white is on pin 46, and the dark blue/white is on pin 20.
In either case the red/white should show 12v all the time, and the dark blue/white whenever the ignition is in run or start position.
Hello again! I have a 60 pin connection, there is a white/red wire on pin 11 and pin 55 no power to pin 11, and 6 volts??? to pin 55.
AnswerHi Ken,
I just can't find any 60-pin pcm plugs in that time frame that has white/red or red/white on 11 and 55. Only one such red/white wire on pin 3. 55 is shown as tan/red and is for the speed control relay; pin 11 is black/tan and a power ground wire, so 6V and no power to those pins seems ok. The color code don't agree with what you say you see.
Aha! I wonder if you are looking at the TCM instead of the PCM? The PCM is hidden under the air intake/filter box, while the TCM is out in the open on the driver side fender. The TCM shows a red/white on 11 and a tan/red on 56, but that is not the module we need to get the engine to start!
Roland
