goldSC400

I have a 94 Sc400 and the other day I was on my way to work and it just died on me at a red light. Since then it will not start up at all. It will crank but will not run. Until this point I have not had any issues with her AT ALL, it ran perfect. First thoughts was it was the fuel pump/fuel pump ecu so tried doing the jumper mod at the pumps ecu, but cannot get power to the ecu anymore. Anyone have any ideas what it could be? Is there a fuse that I could have blown somehow while trying to connect the pump to power? Any help would be greatly appreciated, need my sc back. Thanks.

1SICSC4

My bet is your ecu is going bad.

First thing you need to do is hop in your car and put the key into the on position (don't crank it over). All the lights on you dash should like up like a Christmas tree. If your CEL is not coming on then your ecu is shot. Throw a new ecu in and I bet your car will run!

If you do have a CEL. Then do a diagnostics to see if its throwing any codes.


To retrieve codes, turn ignition on. DO NOT start engine.
Using a jumper wire or paper clip, connect terminals E1 and TE1 together either on
DLC1 or DLC2(diagnostics ports). Count number of flashes from Malfunction
Indicator Light (MIL).

If MIL flashes 2 times every second, system is functioning
properly (no codes present). This is known as a normal condition. If a
diagnostic code is displayed, first group of flashes will indicate
first digit of a 2-digit diagnostic code. After a 1.5 second delay,
second group of flashes will indicate second digit of diagnostic code. (Example would 2 flashes pause then 4 flashes would be 24 AIT sensor signal.)

If more than one code is stored, a 2.5 second delay will
occur between diagnostic codes. After all diagnostic codes have been
displayed, a 4.5 second delay will occur and then codes will be
repeated until jumper wire connecting terminals E1 and TE1 is
disconnected. Diagnostic codes will display from smallest to largest
number.

Identify and record diagnostic trouble codes. After
trouble codes are retrieved, remove jumper wire to exit Normal Mode.

ALL THE ERROR CODES FOR LEXUS AND WHAT THEY MEAN

1 Normal Condition.
2 Air Flow Meter signal.
3 Ignition signal.
4 Engine Coolant Temperature Sensor signal.
5 Oxygen Sensor.
6 RPM signal (Crank Angle Pulse).
7 Throttle Position Sensor signal.
8 Intake Air Temperature Sensor signal.
9 Vehicle Speed Sensor signal.
10 Starter signal.
11 Switch signal.
11 ECU/ECM.
12 Knock Control Sensor signal.
12 RPM signal.
13 Knock Control CPU (ECM).
13 RPM signal.
14 Turbocharger Pressure.
14 Ignition signal.
21 Oxygen Sensor.
22 Engine Coolant Temperature Sensor signal.
23 Intake Air Temperature Sensor signal.
24 Intake Air Temperature Sensor signal.
25 Air-Fuel Ratio Lean.
26 Air-Fuel Ratio Rich.
27 Sub Oxygen Sensor signal.
28 No. 2 Oxygen Sensor signal.
31 Air Flow Meter signal (Vacuum Sensor signal).
32 Air Flow Meter signal.
34 Turbocharger Pressure signal.
35 Turbocharger Pressure Sensor signal.
35 HAC Sensor signal.
41 Throttle Position Sensor signal.
42 Vehicle Speed Sensor signal.
43 Starter signal.
51 Switch signal.
52 Knock Sensor signal.
53 Knock Sensor signal.
54 Inter-cooler ECM signal.
71 EGR System.
72 Fuel Cut Solenoid signal.
78 Fuel Pump Control signal.
81 TCM Communication.
83 TCM Communication.
84 TCM Communication.
85 TCM Communication.

goldSC400

Thanks for your reply. Yea when I turn the power on for the car I have no CEL. So your thinking its the cars ecu or the fuel pump ecu that is bad? For the diagnostic, is that the port under the hood or under the dash? Again thanks a bunch.

1SICSC4

You can use either port for the diagnosis. Its you main ecu thats bad. Its under the passenger side carpet. FYI don't get a ecu form a junk yard chances those ecus are the reason the car is in the yard. If you need one I know a guy that sells them for $150.

When you do the diagnosis I guarantee Your codes are 14 and 15!

BenStoked

iTrader: (3)

before swapping ecus, check the fuses.
its quite possible it's the original fuse, and may have gone bad (fuses do that :/)

1SICSC4

Fuses don't just blow for no reason. If you want to waist time go ahead an check your fuses and relays and wiring and blah blah blah or just be smart and swap the ecu. Its a sc400 the bad ecu is as common as the driver side coil going out. I'm not trying to be a **** but thats just the way it is. When you swap your ecu make sure its from the same year car.

goldSC400

OK, so I checked today, and a 30a fuse for the EFI was blown. Replaced that and bang, power to fuel pump. Car started right up but then died after about 5 seconds. Interesting. Still symptom of ECU being bad?

BenStoked

iTrader: (3)

ecus can and do go bad.
fuses can and do go bad.
experience has taught me both. I have had a fuse blow for no reason, replace it and no problem ever again. I have also had new fuses blow as soon as they were used, and after replacement, the replacement-replacement didn't ever blow...
an ecu is an expensive "test," and I am a cheapskate, so I try to make sure it's the problem before making that investment. fuses and a multimeter are much cheaper, and always usable (a spare ecu, not so much).


goldsc: check the fuse, again, see if it blew, again. if so, see if it blows again. if it does, something definitely needs checking.

goldSC400

Yes that is exactly my thinking, ECU could be bad, but I am a broke college kid so I would like to try to exhaust all other possible fixes first. The fuse that blew is still fine after replacing it, but the car will only turn on, idle EXTREMELY low for a few seconds, then die again. There is also a ticking noise coming from somewhere in the engine whenever the power is key is turned to the on position. If anybody has any ideas on what that could be it would be great. Thank you guys for all your input thus far. UGH, I need my SC back lol

1SICSC4

Have you done the diagnosis to see if your throwing any codes? Start there.

ishootstuf

iTrader: (1)

Wow dude, that's horrible advice! You work at a dealership? That's the kind of stuff my techs used to say all the time.

Yeah, I agree, prolly the ECU - but seriously, don't spend 5 minutes looking at fuses, just spend $150?

1SICSC4

No my first advice was to see if the car is throwing any codes. Anyway if you read post 3 he says he has no CEL with the car in the on position and not running which is a direct sigh of a bad ecu. I dont want to see this kid waist time and be with out his car when the problem is so obvious. And again a fuse will not just go bad. Something has to cause a surge to blow the fuse.

goldSC400

Hey SICSC, where is the MIL supposed to flash? I was out trying to jump the diagnostic port but could not see a light flashing anywhere. Also, the check engine light seems to come on sometimes, but not others, not sure if that means anything yet either.

BenStoked

iTrader: (3)

mil is the one on the gauge cluster, looks like an engine. also known as the check engine light.
is there a pattern as to when the light comes on or doesn't come on?

1SICSC4

Dude please listen to me and swap your ecu. I know it will make your car run and when it does please post. Anyways whats worst spending $150 or not having your car run for a few days.