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91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi)
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Discussion Starter #1
Help. I’ve got a 91 sidekick 4dr 4x4 16v 1.6l manual transmission efi. Throws code for bad tps. 21 and 45. I get sometimes 4.8 volts to start with on the ref wire and then it drops down to as low as 1.5. Runs awful. Ohm ref wire shows fine as do the others. Ground reads good. Have a 4 wire connector. Gy-ground. Bw- throttle. G- back to ecm. Gr-ref wire. Can’t find a mp sensor? Don’t have one?? Cut ref wire back of ecm. Reads same. Key on reads 4.8 at best then falls off in a few min

Help I been at this for a few months now. First time on a forum
 

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99 Tracker, 5 door, 2L, 4x4
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are you reporting the reference voltage at the ECM drops off after a couple of min? keep in mind that some ECU have a common 5vdc buss inside that feeds more than one sensor circuit... normally not shown on external schematics...

You would have to disconnect ALL the sensors to properly test the ECU, before condemning it...
 

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are you reporting the reference voltage at the ECM drops off after a couple of min? keep in mind that some ECU have a common 5vdc buss inside that feeds more than one sensor circuit... normally not shown on external schematics...

You would have to disconnect ALL the sensors to properly test the ECU, before condemning it...
Further thought,
  1. what are you using as test equipment?
  2. Have you disconnected the ECU and checked for a grounded circuit (must be loaded).. apply power through a test light, monitor with a scope or graphing meter...watch for heat related creep.. cannot be monitored with DVOM...
 

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91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi)
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Discussion Starter #4
Thanks

I didn’t know it fed other sensors also. I can just check for any other wires out of the back of the ecm that have 5 volts key on? Or do I have to run it to check. Then pull those sensors? Or ALL sensors?
 

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If you are losing the ref, any sensor on that circuit or buss that grounds will drop the ref voltage, that will also involve any stray circuit grounds..
 

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91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi)
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Discussion Starter #6
Roger.

I will check that out n get back to you. Messn with this on nights n weekends in between working and trying to build my house up here n the ak so might take me a bit. Pretty new to wire tracing. I’ve always avoided it like the plague but I’m all by myself on this one so bear with me.

Many thanks
 

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Code 21 is high voltage found when the engine is idling. The signal voltage for the TPS is not static at 5v, it changes from 0.5v at idle to 5v at wide open throttle, so much depends on the position of your gas pedal.
Code 45 is the idle circuit - and the code, among other things, means that your idle switch is on, but that your gas pedal is depressed somewhat (meaning that the engine is not idling). You may want to first start with recalibration of the TPS
 

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91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi)
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Discussion Starter #8
Bex. Thanks

Quick riddle me this. It’s my 5volt ref wire having trouble with. Won’t stay at 5 or close. Falls off. Have wire cut just out of the ecu and sensor unplugged. So regardless of adjusted tps or not i should have a steady 5ish volts on that ref wire. Right?
 

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The gray/red wire will show the 5v reference all the time. The gray wire is the TPS signal and that will vary between 0.5v and 5v depending on the position of the throttle. A fast test from the FSM - clear your codes, disconnect the TPS sensor, start the engine and let it run until the CEL comes back on. Do you still have the code 21 (high voltage) or has it now switched to a code 22 (low voltage - which is what you should get now). If the code remains at a code 21, then you have a voltage source shorted to the gray wire somewhere in the circuit.
 

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Bex. Thanks

Quick riddle me this. It’s my 5volt ref wire having trouble with. Won’t stay at 5 or close. Falls off. Have wire cut just out of the ecu and sensor unplugged. So regardless of adjusted tps or not i should have a steady 5ish volts on that ref wire. Right?
Correct! Some ECU are spike protected so if there is a short or ground on the circuit, they will shut down the reference.

Open circuit will be high ~5vdc,
short/ground will exhibit < than the reference..
 

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91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi)
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Discussion Starter #11
Ok ok


I think I’m getting my head wrapped around this. Thanks to you guys. One last question hopefully. Bex. I have ohmed out the grey wire. The one aforementioned that reads .5v to 5 volts. It ohms out fine. You said that one of the other circuits is shorted to the grey wire? So two questions guess.
1. If I Jump the grey wire from the ecu to the tps then the tps should work right?
2. Would the grey wire ohm out ok if another POWER wire was shorted to it??......... like I said I’m new at the wire tracing game

It does stay with the 21 code
 

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Typically using an Ohm meter to check for continuity may not prove a good circuit, the low ma from the meter can be carried by a single strand, whereas a load of 3-5 amps will fail.. It is always better served to test circuits loaded...

DO NOT fall into the trap of jumping wires, many ECU have suffered catastrophic failures with this procedure..
 

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I used the wire colors, so that we’re sure we’re talking about the same wiring. It’s the grey/red wire that is the 5v reference - you’re advising that it does not stay at 5v - is that correct? The other wire (the gray wire) which is the TPS signal fluctuates voltage, as it should, depending on the throttle position. The grey wire only feeds the TPS (TPS signal only). The grey/red wire (5v reference) feeds not only the TPS, but also the MAP sensor. If you are losing the 5 reference, then we are talking about the grey/red wire.

And x2 to Aqua’s last sentence.....
 

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91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi)
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Discussion Starter #14
Merry Christmas you guys!

Im back at this thing here. Thanks for y’alls help. I need more? I’m stuck again. Yes it’s def the grey/red wire that just won’t keep 5 volts. Starts off around 4.9 and then just falls off with key on. I get what y’all are saying. That is test other sensors and wires to them that share same ground. Having trouble finding any kind of wiring diagram that fits my car. I have a 4 wire tps. Grey/yellow- ground. Grey- is throttle switch wire back to ecu. Blue white wire- I forget now... Grey/red wire is my ref voltage. Near as I can tell there is only one other sensor that uses that grey/yellow-ground and it tests fine. Not a hundred percent sure how to load test so I tested the power wire to that sensor for ground by looking for a voltage reading using a known power source then trying to get a voltage reading by completing the circuit if the power wire was grounding out. Got nothing with the sensor unplugged. As far asI can tell I don’t have a map sensor. like I said at one point I cut the grey/red wire right out the back of the ecu just in case I missed the map sensor and It still did same. I’m lost again. Any chance you guys know where I could find a accurate wiring diagram for this car. I’ve looked and looked and they all show a 3 wire tps. As far as I know it’s a 91 sidekick built in dec. 16v mpi 4 door manual 4wheeldrive. And I misspoke when I said jump. I meant run a new wire from ecu to tps

thanks for y’all’s time and help
 

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This probably won’t help, but my TPS is also 4 wired:
95251
 

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Or this:
95252
 

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Hope that "known good power source" was not anything >ref voltage..

If you look at the last schematic supplied by BEX, you will see a number of terminals "5v REF", they are all common internal to the ECU. Any anomaly on those circuits will affect all the others... Ground shorts, high resistance (wire/connections), bad sensors...
 

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91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi)
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Discussion Starter #18
Ok guys

Does it make any sense that I don’t have
1- map sensor
2-intake air temp. Sensor
3- thanks to BEX i saw California only on the egrt sensor——. Do have the connector next to the tps and did check that

All I can find are
-4 tps wires.
  • 2 egrt wires. Red/green. And the grey/yellow
  • ect. 2 wires. The grey/yellow and red/yellow

ohmed out all of these wires and they read perfect. Tested them for short n got nutn. Pulled the tps and ect sensor.—still fall off on the ref wire?‍♂ Grounded the grey yellow wire and still nutn

What am I missing. Or how many things am I missing. Thanks again
 

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What market was your car made for? Only the California market, in 1991, would have the ‘REGTS’ temp sensor in the EGR valve. So I assume that your car is for the California market. However, as far as I know, all the 1991 vehicles would have a MAP sensor (gray/green wire - small sensor that is screwed into the firewall on the passenger side) and an IAT sensor (red/black wire, diagonally above the coolant temp sensor)???

All the sensors that you are listing use the gray/yellow wire as their ground.....You may want to try this simple test - clear your codes (remove the dome light fuse for a minute), then disconnect the TPS connector and start the car. The CEL should come on shortly afterward - does it still throw the code 21, or has it now changed to a code 22??
 

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91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi)
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Discussion Starter #20
Roger.

Thanks Bex. I’ll look again for the map. I did not look on the firewall. Also for the iat but if it’s there then I got a super bad case of man eyes. These sensors should all have the grey/yellow wire with them right? I tried determining if I had these sensors by looking for the same colored wire at the back of the ecu where the wire harness plugs in and I did not find a grey/green wire or the red/black wire. I’ll check again though and let you know. I am in AK so it makes good sense that this lil beauty could be from ca but. I only have the plug in for the regts sensor. t’d out next to the tps. No sensor?‍♂ And I’ll try checking the codes again and let you know

Many thanks again
 
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