89' 740 GL Wagon still coding 1-2-3 after both ETC replaced

POsubVolvo · Post by **POsubVolvo** » 23 Apr 2009, 07:19

I have a 89 740GL Wagon with a B230 engine and 263,000 miles.
My code was reading Engine coolant temp sensor (1-2-3) so I have replaced both ECT sensors. I Removed the intake manifold to get to the back sensor and replaced the intake manifold gasket torquing the nuts to 15lb. It is still coding 1-2-3 with a cold start problem. In the morns the car will crank and catch then die. I have to turn the key for quite some time before it will hold the idle long enough for me to put it into gear and go- which can take 5-10 minutes. If during that time I press the gas pedal it will die. I've replaced the MAF sensor and sometimes will unplug it if the car doesn't start after the first try. It will usually start then and hold a rougher idle. If I plug the MAF sensor back before it gets warm enough, it will die again. Once I drive it it will start again right away throughout the day. There is an exception to this because randomly (every few months) I'll be driving it for 3 hours straight, stop at a convience store for a few minutes, go to crank the engine and get nothing. I then get someone to give me a jump and it's runs for another 3 hours and is fine for another few months. I don't know if this is a secondary problem or connected to my cold start problem. The most recent repair was replacing a broken tensioner, timing belt and timing belt covers. Between 231,000 - 263,00 miles we have replaced: Both Coolant temp sensor and rebuilt the wires to the ECT guage sensor, MAF sensor and air flow tube, Battery, Battery cables & assembly wires, impulse wire, engine speed sensor, new altenator and rebuilt the frayed ground wire, thermostat, 3 fuel injector seals, rebuilt trans & trottle valve cable, interior & exterior fuel pumps & filters, ignition coil, water pump and all 4 belts, platinum spark plugs gently gapped to .65, new radio w/2 speakers, PVC Flame trap & nipple. FYI: I picked up a 99 Turbo Wagon w/120,000 the same color as mine for mostly body parts. It was rear ended and the guy hit a deer with the front end but he drove it home and it was parked for 5 years before I bought it. Telling you this to let you know I possibly have a resource to pull parts to test out possible fixes. I'm a sub for the P.O. for 1.5 yrs which had been hard on my vehicle and most of the above repairs have been done then. My husband and I try to do as many repairs as we can ourselves. Last week, I took it to a Volvo dealer out of frustration when it kept coding 1-2-3 with the cold start problem. They wanted to replace the MAF but we did it ourselves since I really didn't think that would solve the problem and it hasn't.

Post by **billofdurham** » 23 Apr 2009, 16:01

Welcome to Matthew's Volvo Site.

It would seem that you have just about rebuilt the car and, in the process, covered most of the things that would cause this problem.

One question to start - do you erase the code every time you do something to sort this?

1-2-3 is set when the ECU interprets the signal from the engine coolant temp (ECT) sensor as below -40C or above 120C. The control module then assumes an engine temperature of 20C at startup or 90C when running to allow the car to be driven in limp home mode. Possible sources for the problem are open circuit or short circuit to earth (ground) in the cables, terminals or the sensor, contact resistance in the terminals or a poor earth terminal for the signal earth.

Have you tested for voltage at the sensor connector? Using a voltmeter with the sensor disconnected and ignition on test between terminal 1 on the connector and earth. The voltage should be approx 5v. Terminal 1 is the right hand one looking at the connector. As you have replaced the sensor testing for resistance would appear to be redundant.

Bill.

POsubVolvo · Post by **POsubVolvo** » 23 Apr 2009, 16:58

Thanks for the reply! I reset the code by disconnecting a battery terminal and leaving it off for 15+ minutes every time I do a coding repair. Hopefully this is correct? It shows no code initially till the car gives me trouble cold starting again. My husband is the electronics guru and has a mutimeter. I will see if he can check the electrical connections with that. I just purchased a Haynes Tech book to help with codes and checking electrical connections but alot of it is still Greek to me. Reading my Chilton's manual and some of the posts, I was wondering if it could be the cold start valve or the radio suppression relay? I can't locate where the radio suppression relay is located in my manual or it's function. Oct 08 a mechanic said it needed a throttle control sensor. We never replaced it and it never coded that for us when we checked the black box coding device. Yes we have practically rebuilt the car since I only included the repairs I thought would be pertinent to the current problem. More recently, I've begun to use only Volvo parts and order them from a place in Atlanta that I've found to be the cheaper then most after market parts.

POsubVolvo · Post by **POsubVolvo** » 24 Apr 2009, 11:59

We plan to check the ECT sensor's resistance and the plug's voltage tonight. Saw a 1/13/07 post by billofdurham about checking the code in both #2 & #6 sockets. I didn't know about #6 so I just checked it and it codes 2-2-4 = ECT sensor also. Will let you know what we find out.
Thanks

Post by **billofdurham** » 24 Apr 2009, 12:26

That is one way of erasing codes, although it doesn't always do it. The correct way is in the attached as is the location of the radio suppression relay for both of the cars you have.

740 erasing fault codes.pdf: (59.75 KiB) Downloaded 405 times

The radio suppression relay (as it's called) is actually a fuel injector relay. The pre 1986 injectors were supplied constant + power to one terminal and supplied a timed ground to the other terminal via the ECM. The constant + power used to come from the fuel pump/injection system relay. In 1986 Volvo decided to isolate the fuel injector circuit because of some radio interference created by the pulsing circuit. The solution was to energize a relay (the radio suppression relay) with the pump/system relay feed instead of using it to power the injectors directly. The radio suppression relay then supplies the + power to the injectors. The timed ground still comes from the ECM. However, this relay usually causes problems on hot starts.

You also mention the throttle switch. It may be out of adjustment or it may be faulty. Here's another one for your husband to test.

740 throttle switch testing.pdf: (66.23 KiB) Downloaded 454 times

As you have replaced the ECTs it may pay to erase the code 2-2-4 as above and see if that one returns.

Bill.

POsubVolvo · Post by **POsubVolvo** » 29 Apr 2009, 12:23

Found the problem! The "new" engine coolant temperature sensor that I bought for $68 from a Volvo dealership has no ohm reading. It's taken me a month to discover this. I first checked the electrical lead connector to the ETC sensor and the voltage was fine. When my husband & I checked the flat prongs coming out of the ECT sensor on the ohm setting of our meter we got nothing. I had the key in the on position when we did this. Hope that was correct.
Current problem: I picked up an $18 after market ECT and can't get my 19mm open end wrench around it plus there isn't any room to move the wrench. That's why last time I replaced it I took off the Intake manifold to get to the ECT sensor and replaced the manifold gasket . Is there some secret I should know to avoid taking off the Intake manifold? If I do have to remove the manifold will I need to replace the gasket again? It was done about 1 month ago. By the way, after clearing the codes as you instructed, now only port #6 codes ECT sensor. Port #2 cleared its ECT sensor code. Once I replace the ECT sensor this time, I will clear the codes again.

Post by **billofdurham** » 29 Apr 2009, 16:15

When my husband & I checked the flat prongs coming out of the ECT sensor on the ohm setting of our meter we got nothing. I had the key in the on position when we did this. Hope that was correct.

It doesn't matter as you would have the connector off so no power going to the sensor.

It is possible to change the sensor without removing the intake, it's just a little fiddly.

Use a regular 19mm 12pt 1/2" drive socket with an adapter to 3/8" drive and a long 3/8" drive wobble extension. Next pull off the IAC hose from the intake manifold and pull it aside so you can extract the sensor through that opening. Once the sensor is loose reach in with some very long needle nose pliers and pull it out, using a long screwdriver to keep the copper sensor washer in place so it doesn't fall down and get lost as replacement sensors don't usually come with a new washer.

So what is a wobble bar extension? This link shows a Draper but you should be able to pick up a different make easily.

http://www.draper.co.uk/Pages/Pagesource/p40.pdf

Bill.

POsubVolvo · Post by **POsubVolvo** » 29 Apr 2009, 19:05

Thanks. The 19mm 12pt socket fits over the new after market sensor but not over the Volvo sensor, it's deeper and all the 12pt deep well sockets I've found have a ridge inside that prevents me from getting the socket deep enough to get a grip on the "Volvo" sensor. I will look again tomorrow for a 19mm deep well without the ridge inside.

POsubVolvo · Post by **POsubVolvo** » 08 May 2009, 06:44

Last night we finally got around to putting in the after market ECT sensor with copper washer and a bright blue plastic casing over the prongs. Knowing that 89 has a black plastic casing and 88 and below a blue plastic casing, I questioned the accuracy of the part. The parts store assured me that was the one that came up on their computer for my 89'. The ECT I pulled out last night was a Volvo part with a black plastic casing w/ no copper washer. Had to take off the intake manifold again to get it out. The 19mm 12pt wasn't deep enought so we even tried grinding the ridge out of a 3/4" deep well socket that fit over the ECT sensor with no success. We installed the new sensor that came with a copper ring, we reread the codes before trying to clear them: port #2 coded clear but port # 6 still coded 2-2-4 =ECT sensor. I preformed the steps to clear the codes that you gave me, disconnected the battery for a minute, then reconnected it, checked the codes again to see if they were cleared and port # 6 is still reading 2-2-4. My plan is to now take the Volvo ETC sensor I bought from the dealership, have them test it with a stronger meter, ours is a small one battery volt/ohm meter. If it is bad they said they will order me a new one. Let me know if you can think of anything else that I can check. Remember we checked voltage coming from the electric plug to the sensor I got voltage coming from both ports. With metal connector clip at the top, the right one read 5.4v and the left one read 4.? volts. So, I think that it is fine.

Post by **billofdurham** » 08 May 2009, 12:32

This question may seem impertinent but when you clear the codes are you clearing them in both ports?

Bill.