
96 Mich. App. 683 (1980)
293 N.W.2d 676
VANDERBERG
v.
GENERAL MOTORS CORPORATION
Docket Nos. 77-2616, 77-2617.
Michigan Court of Appeals.
Decided April 21, 1980.
Reamon, Williams, Klukowski, Wood & Drew, P.C., for plaintiff.
Dykema, Gossett, Spencer, Goodnow & Trigg (by Donald E. Shely and Kathleen McCree Lewis) and Seymour, Seymour, Conybeare & Straub (Otis M. Smith and John P. Raleigh, of counsel), for General Motors Corporation.
Lilly, Piatt & Doyle, for Boylan Buick, Inc.
*686 Before: D.F. WALSH, P.J., and R.B. BURNS and J.H. GILLIS, JJ.
R.B. BURNS, J.
On March 19, 1970, plaintiff John L. Vanderberg, was driving at a speed of approximately 70 miles per hour along I-94 in Berrien County. While traveling in the right lane of the roadway, plaintiff came upon a slower moving tractor-trailer truck. Plaintiff signaled and pulled out to pass the truck. When the truck driver flashed his lights to indicate that plaintiff was safely passed, plaintiff again signaled and reentered the right lane. Plaintiff's vehicle failed to straighten out in the right lane. The car straddled the guardrail and rode it into an underpass. Plaintiff's wife, a passenger in the vehicle, was killed instantly and plaintiff was seriously injured.
Plaintiff alleges that the accident occurred because carbon monoxide leaked from the exhaust system of the vehicle, a Buick Electra, into the passenger compartment, causing plaintiff to lose consciousness. Plaintiff brought suit against defendant General Motors Corporation on claims that the defendant had breached an implied warranty by producing a defective vehicle and that the defendant had been negligent in failing to design, engineer and manufacture an exhaust system that would safely carry exhaust fumes away from the vehicle's passenger compartment.
The Vanderberg automobile was leased from defendant Boylan Buick under a full maintenance lease. Against defendant Boylan plaintiff asserted claims that the defendant had breached an implied warranty in leasing a defective vehicle and that the defendant was negligent in failing to discover areas of leakage when defendant made periodic repairs and maintenance of the vehicle.
*687 The matter was tried before a jury. At the close of plaintiff's proofs, the trial court directed verdicts in favor of both of the defendants. Plaintiff appeals.
Plaintiff maintains that the trial court erred in excluding evidence which plaintiff sought to introduce in support of his claim that he suffered carbon monoxide poisoning. The court admitted into evidence a hospital report which indicated that carbon monoxide was found in plaintiff's blood. This ruling was based on a finding that the evidence was "qualitative" and therefore admissible as a description of a physical condition. The court, however, excluded the deposition testimony of plaintiff's physician to the extent that the doctor relied on the records of any quantitative carbon monoxide tests. The court held that this "quantitative" evidence was a diagnosis and thus inadmissible.
We do not agree that the "quantitative" test results were a diagnosis. The evidence appears to be a factual statement of an observed condition and not an inadmissible diagnosis. Moreover, the treating physician should have been permitted to testify with regard to the analytical data underlying his diagnosis. Alexander v Covel Manufacturing Co, 336 Mich 140; 57 NW2d 324 (1953). Nevertheless, the error does not constitute grounds for reversal as there was other competent evidence which supported plaintiff's claim that he was afflicted with carbon monoxide poisoning.
Plaintiff also maintains that error occurred when the trial court struck testimony regarding a test that was performed on the Vanderberg vehicle's exhaust system. Shortly after the alleged incident, Dr. Charles Nagler, a forensic science expert, conducted a test to determine whether *688 there were leaks in the vehicle's exhaust system. The test procedure was similar to that used to identify leaks in automobile tires, and Dr. Nagler testified that when using this test he observed leaks in the exhaust system.
Though the only relevancy the leak test could have had would be as an indicator that the areas that leaked could emit carbon monoxide in the normal operation of the vehicle, the test was made under conditions which did not attempt to simulate the operation of the system during actual driving conditions. Based on the test's failure to simulate actual vehicle operation conditions, the trial court granted defendants' motion to strike the testimony regarding the test.
The admission or exclusion of test results is within the trial court's discretion. We do not interfere with the court's ruling in this regard unless an abuse of that discretion is clearly evident. Smith v Grange Mutual Fire Ins Co of Michigan, 234 Mich 119, 127; 208 NW 145 (1926). As it is commonly required that testing procedures be conducted under conditions similar to those in the occurrence in question, the trial court did not abuse its discretion in striking Dr. Nagler's testimony regarding the test. Elliott v A J Smith Contracting Co, Inc, 358 Mich 398, 417; 100 NW2d 257 (1960), Smith, supra, 127.
Plaintiff's final and principal claim on appeal is that the trial court erred in granting directed verdicts in favor of both defendants.
In reviewing the decision of the trial court to grant the motions for directed verdict, we bear in mind that:
"The jury, not the trial judge, is the trier of fact. Whenever a fact question exists, upon which reasonable *689 persons may differ, the trial judge may not direct a verdict. Conversely, when no fact question exists, the trial judge is justified in directing a verdict." Caldwell v Fox, 394 Mich 401, 407; 231 NW2d 46 (1975).
In order to determine whether a fact question exists, this Court will "view the testimony in the light most favorable to the plaintiff and draw the reasonable inferences therefrom which are in his favor". Caldwell, supra, 407. We do so because, as the Supreme Court long ago stated, plaintiff:
"* * * had a right to ask the jury to believe the case as he presented it; and, however improbable some portions of his testimony may appear to us, we can not say that the jury might not have given it full credence. It is for them, and not for the court to compare and weigh the evidence." Detroit & M R Co v Van Steinburg, 17 Mich 99, 117 (1868), cited at Caldwell, supra, 407.
To withstand the motions for directed verdict in this case, plaintiff must have produced evidence of a defect in the vehicle's exhaust system, evidence which shows a causal connection between the defect and injuries suffered by plaintiff, and evidence which establishes that the defect is attributable to either or both of the defendants.[1]Caldwell, supra, 410. Plaintiff need not isolate the specific cause of the defect to avoid a motion for directed verdict, but he must present sufficient evidence, either circumstantial or direct, "from which the jury could reasonably infer that some defect in manufacture caused the accident". Holloway v General Motors Corp (On Rehearing), 403 Mich 614, 618; 271 NW2d 777 (1978).
With respect to the claim of negligent maintenance *690 against defendant Boylan, plaintiff must produce evidence of a duty owed by Boylan to plaintiff, evidence of a breach of that duty by Boylan, and evidence showing a causal relationship between the breach of duty and injuries suffered by plaintiff.
Defendants assert that the proofs offered by plaintiff support neither a reasonable inference that a defect existed nor a reasonable inference that a defect attributable to the manufacturer or lessor caused the accident. Defendant Boylan further maintains that the proofs do not support a reasonable inference that negligent maintenance by it caused the accident. We agree.
Based on the evidence presented, the jury could have reasonably determined that plaintiff was overcome by carbon monoxide poisoning and that this condition caused plaintiff to black out, in turn causing plaintiff's vehicle to leave the roadway and collide with the underpass. But at this point, plaintiff's proofs meet an unbridgeable gap. There is no evidence from which the jury could reasonably infer that emissions traveled from the vehicle's exhaust system into the passenger compartment because of a defect inherent in the exhaust system. Unlike the ball joint assembly discussed in Holloway, supra, the exhaust system is expected to wear out and be replaced. Because of its exposed position it is also subject to sudden damage from impact with objects on the road. A failure of the system to function properly does not in itself necessarily establish a latent structural defect. The accident may have occurred because of damage to the exposed exhaust system after the vehicle left the hands of the manufacturer, defendant General Motors, and after the last maintenance or repair conducted by defendant Boylan.
*691 Since, after all the evidence is considered, there exist two or more equally plausible explanations as to how carbon monoxide might have leaked into the passenger compartment, the selection by the jury of one explanation over the other would be based not on a reasonable inference but on conjecture. See Meli v General Motors Corp, 37 Mich App 514, 518; 195 NW2d 85 (1972).
The trial court was correct in ruling that plaintiff had not met his burden of proof in this action.
Affirmed. Costs to defendants.
J.H. GILLIS, J., concurred.
D.F. WALSH, P.J. (dissenting).
I must dissent. The existence of a defect, attributable to the manufacturer, in an automobile's exhaust system as well as negligent maintenance of that exhaust system are provable by circumstantial evidence. Holloway v General Motors Corp (On Rehearing), 403 Mich 614; 271 NW2d 777 (1978), Caldwell v Fox, 394 Mich 401; 231 NW2d 46 (1975). The test is whether the evidence takes the case out of the realm of conjecture and supports legitimate inferences from established facts. Weisenberg v Village of Beulah, 352 Mich 172; 89 NW2d 490 (1958).
In this case it seems to me that there is convincing evidence that a defective exhaust system in the leased 1969 Buick Electra driven by plaintiff, John L. Vanderberg, caused the introduction of carbon monoxide gas into the passenger compartment of the vehicle, and that the presence of the carbon monoxide caused Vanderberg to pass out and lose control of the vehicle with the result that the vehicle left the paved portion of the highway and struck a concrete overpass abutment.[1]
*692 The automobile was only 13 months old, had been driven less than 19,000 miles and had been regularly serviced by Boylan Buick, Inc., under the terms of the leasing agreement. It may be, as the majority points out, that an automobile's factory installed exhaust system cannot be expected to last for the life of the automobile. A jury could reasonably conclude, however, that an exhaust system which wears out to the point of serious and dangerous malfunction after just 13 months of normal use and in less than 19,000 miles was defective when it was installed at the factory.
Certainly, as the majority also points out, the defective condition of the exhaust system could have been caused by something other than normal use. Someone may have tampered with the system or the car may have been in a previous accident. In this case, however, there is no evidence whatsoever that the exhaust system was subjected to any potentially damaging condition other than normal use. Moreover, the plaintiff did not have the burden of eliminating every other plausible explanation for the defect. As the Supreme Court stated in Holloway v General Motors Corp (On Rehearing), supra, 621-622:
"A plaintiff has the burden of establishing that when the product left the manufacturer it was defective. He is not, however, obliged to eliminate all possible causes of the accident consistent with the view that there was no manufacturing defect. He sustains his burden when *693 he establishes with direct or circumstantial evidence a reasonable probability that the defect is attributable to the manufacturer.
"On a motion for directed verdict, the question is whether it is reasonable to infer from the evidence, direct or circumstantial, that the accident was probably caused by a defect attributable to the manufacturer. Questions of comparative probability are to be resolved by the trier of fact. As stated in Schoepper v Hancock Chemical Co, 113 Mich 582, 586, 589; 71 NW 1081 (1897), and since reaffirmed in Schedlbauer v ChrisCraft Corp, 381 Mich 217, 230-231; 160 NW2d 889 (1968):
"`It is true that where an injury occurs that cannot be accounted for and where the occasion of it rests wholly in conjecture, the case may fail for want of proof. * * * But such cases are rare, and that rule should never be so extended as to result in a failure of justice, or in denying an injured person a right of action where there is room for balancing the probabilities, and for drawing reasonable inferences better supported upon one side than upon the other. * * * [T]he question of whether the inference suggested by the plaintiff's theory is the correct one, or whether it was sufficiently rebutted, was for the jury.' (Emphasis supplied.)"
Plaintiff Vanderberg testified that during the winter of 1969-1970 he became fatigued during long trips in the leased Buick. From this testimony the jury could find that the defective condition in the exhaust system existed prior to the end of December 1969. Defendant Boylan had the car for inspection and servicing on December 30, 1969, and January 23, 1970. There was sufficient circumstantial evidence, therefore, for the jury to conclude that defendant Boylan was negligent in failing to repair the defective exhaust system.
I would reverse the trial court and remand for a new trial.
NOTES
[1]  These elements apply not only to plaintiff's product liability claims based on breach of warranty but also to his product liability claim against General Motors which sounds in negligence.
[1]  The testimony of plaintiff Vanderberg together with that of the medical experts established that the carbon monoxide level in Vanderberg's blood immediately after the accident was in excess of 30% and possibly as high as 40% to 50% and that Vanderberg's only exposure to an established source of significant levels of carbon monoxide was the exhaust system of the Buick Electra manufactured by defendant General Motors and leased from and maintained by defendant Boylan Buick, Inc.
